Review Article Current Status and Future Prospects of the...

Review ArticleCurrent Status and Future Prospects of the SNO+ Experiment

S Andringa1 E Arushanova2 S Asahi3 M Askins4 D J Auty5 A R Back26 Z Barnard7

N Barros18 E W Beier8 A Bialek5 S D Biller9 E Blucher10 R Bonventre8 D Braid7

E Caden7 E Callaghan8 J Caravaca1112 J Carvalho13 L Cavalli9 D Chauhan137

M Chen3 O Chkvorets7 K Clark369 B Cleveland714 I T Coulter89 D Cressy7

X Dai3 C Darrach7 B Davis-Purcell15 R Deen89 M M Depatie7 F Descamps1112

F Di Lodovico2 N Duhaime7 F Duncan714 J Dunger9 E Falk6 N Fatemighomi3

R Ford714 P Gorel5 C Grant4 S Grullon8 E Guillian3 A L Hallin5 D Hallman7

S Hans16 J Hartnell6 P Harvey3 M Hedayatipour5 W J Heintzelman8 R L Helmer15

B Hreljac7 J Hu5 T Iida3 C M Jackson1112 N A Jelley9 C Jillings714 C Jones9

P G Jones29 K Kamdin1112 T Kaptanoglu8 J Kaspar17 P Keener8 P Khaghani7

L Kippenbrock17 J R Klein8 R Knapik818 J N Kofron17 L L Kormos19 S Korte7

C Kraus7 C B Krauss5 K Labe10 I Lam3 C Lan3 B J Land1112 S Langrock2

A LaTorre10 I Lawson714 G M Lefeuvre6 E J Leming6 J Lidgard9 X Liu3 Y Liu3

V Lozza20 S Maguire16 A Maio121 K Majumdar9 S Manecki3 J Maneira121 E Marzec8

A Mastbaum8 N McCauley22 A B McDonald3 J E McMillan23 P Mekarski5 C Miller3

Y Mohan8 E Mony3 M J Mottram26 V Novikov3 H M OrsquoKeeffe319 E OrsquoSullivan3

G D Orebi Gann81112 M J Parnell19 S J M Peeters6 T Pershing4 Z Petriw5 G Prior1

J C Prouty1112 S Quirk3 A Reichold9 A Robertson22 J Rose22 R Rosero16 P M Rost7

J Rumleskie7 M A Schumaker7 M H Schwendener7 D Scislowski17 J Secrest24

M Seddighin3 L Segui9 S Seibert8 T Shantz7 T M Shokair8 L Sibley5 J R Sinclair6

K Singh5 P Skensved3 A Soumlrensen20 T Sonley3 R Stainforth22 M Strait10

M I Stringer6 R Svoboda4 J Tatar17 L Tian3 N Tolich17 J Tseng9 H W C Tseung17

R Van Berg8 E Vaacutezquez-Jaacuteuregui1425 C Virtue7 B von Krosigk20 J M G Walker22

M Walker3 O Wasalski15 J Waterfield6 R F White6 J R Wilson2 T J Winchester17

A Wright3 M Yeh16 T Zhao3 and K Zuber20

1 Laboratorio de Instrumentacao e Fısica Experimental de Partıculas (LIP) Avenida Elias Garcia 14 1∘ 1000-149 Lisboa Portugal2 School of Physics and Astronomy Queen Mary University of London 327 Mile End Road London E1 4NS UK3 Department of Physics Engineering Physics amp Astronomy Queenrsquos University Kingston ON Canada K7L 3N64 University of California 1 Shields Avenue Davis CA 95616 USA5 Department of Physics University of Alberta 4-181 CCIS Edmonton AB Canada T6G 2E16 Physics amp Astronomy University of Sussex Pevensey II Falmer Brighton BN1 9QH UK7 Laurentian University 935 Ramsey Lake Road Sudbury ON Canada P3E 2C68 Department of Physics amp Astronomy University of Pennsylvania 209 South 33rd Street Philadelphia PA 19104-6396 USA9 University of Oxford The Denys Wilkinson Building Keble Road Oxford OX1 3RH UK10The Enrico Fermi Institute and Department of Physics The University of Chicago Chicago IL 60637 USA11Department of Physics University of California Berkeley CA 94720 USA12Lawrence Berkeley National Laboratory Nuclear Science Division 1 Cyclotron Road Berkeley CA 94720-8153 USA13Laboratorio de Instrumentacao e Fısica Experimental de Partıculas and Departamento de Fısica Universidade de Coimbra3004-516 Coimbra Portugal

14SNOLAB Creighton Mine No 9 1039 Regional Road 24 Sudbury ON Canada P3Y 1N2

Hindawi Publishing CorporationAdvances in High Energy PhysicsVolume 2016 Article ID 6194250 21 pageshttpdxdoiorg10115520166194250

2 Advances in High Energy Physics

15TRIUMF 4004 Wesbrook Mall Vancouver BC Canada V6T 2A316Brookhaven National Laboratory Chemistry Department Building 555 PO Box 5000 Upton NY 11973-500 USA17Center for Experimental Nuclear Physics and Astrophysics and Department of Physics University of Washington SeattleWA 98195 USA

18Norwich University 158 Harmon Drive Northfield VT 05663 USA19Physics Department Lancaster University Lancaster LA1 4YB UK20Institut fur Kern- und Teilchenphysik Technische Universitat Dresden Zellescher Weg 19 01069 Dresden Germany21Departamento de Fısica Faculdade de Ciencias Universidade de Lisboa Campo Grande Edifıcio C8 1749-016 Lisboa Portugal22Department of Physics University of Liverpool Liverpool L69 3BX UK23Department of Physics and Astronomy University of Sheffield Hicks Building Hounsfield Road Sheffield S3 7RH UK24Department of Chemistry amp Physics Armstrong Atlantic State University 11935 Abercorn Street Savannah GA 31419 USA25Instituto de Fısica Universidad Nacional Autonoma de Mexico (UNAM) Apartado Postal 20-364 01000 Mexico DF Mexico

Correspondence should be addressed to V Lozza valentinalozzatu-dresdende

Received 22 July 2015 Accepted 22 November 2015

Academic Editor Vincenzo Flaminio

Copyright copy 2016 S Andringa et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited Thepublication of this article was funded by SCOAP3

SNO+ is a large liquid scintillator-based experiment located 2 kmunderground at SNOLAB Sudbury Canada It reuses the SudburyNeutrino Observatory detector consisting of a 12m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pureliquid scintillator Designed as a multipurpose neutrino experiment the primary goal of SNO+ is a search for the neutrinolessdouble-beta decay (0]120573120573) of 130Te In Phase I the detectorwill be loadedwith 03natural tellurium corresponding to nearly 800 kgof 130Te with an expected effective Majorana neutrino mass sensitivity in the region of 55ndash133meV just above the inverted masshierarchy Recently the possibility of deploying up to ten times more natural tellurium has been investigated which would enableSNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future AdditionallySNO+ aims tomeasure reactor antineutrino oscillations low energy solar neutrinos and geoneutrinos to be sensitive to supernovaneutrinos and to search for exotic physics A first phase with the detector filled with water will begin soon with the scintillatorphase expected to start after a few months of water data taking The 0]120573120573 Phase I is foreseen for 2017

1 Introduction

SNO+ is a large-scale liquid scintillator experiment located ata depth of 5890 plusmn 94meter water equivalent (mwe) in ValersquosCreighton mine in Sudbury Canada The deep undergroundlocation the high purity of materials used and the largevolumemake SNO+an ideally suited detector to study severalaspects of neutrino physics

The main goal of SNO+ is a search for the neutrinolessdouble-beta decay (0]120573120573) of 130Te 0]120573120573-decay is a rarenuclear process that will happen if neutrinos are Majorana-type particles that is they are their own antiparticlesUnderstanding the Majorana nature of neutrinos is one ofthe most active areas of research inmodern neutrino physicsTheobservation of the 0]120573120573-decaywould demonstrate leptonnumber violation a key ingredient in the theory of leptogen-esis The process can be seen as two simultaneous 120573-decaysin which two neutrons are converted into two protons andtwo electrons as the neutrinos from the two weak verticesmutually annihilate The signature is a peak at the 119876-valueof the process in the summed energy spectrum of the twoelectrons The measured quantity is the half-life of the decayThe effective Majorana neutrino mass 119898

120573120573 which is highly

dependent on the nuclear matrix elements is derived fromthe half-life as described in [1] A half-life of the order of 1025

years corresponds to a neutrino mass range of about 200ndash400meVThe large mass and low background of SNO+ allowthe investigation of such a rare event

The large volume and the high radio-purity are also thereason why SNO+ can explore several other physics topicsObservation of geoneutrinos will help in understandingthe mechanisms for heat production in the Earth Reactorantineutrino measurements constrain the neutrino oscilla-tion parameters Neutrinos and antineutrinos coming fromsupernova explosions would help to answermany unresolvedquestions in neutrino astronomy Additionally SNO+ has thepotential to search for exotic physics like axion-like particlesand invisible nucleon decay

The depth of SNOLAB also provides the opportunityto measure low energy solar neutrinos like pep and CNOneutrinos The pep neutrinos are monoenergetic with anenergy of 144MeV and a very well predicted flux with anuncertainty of 12 constrained by the solar luminosity [2]A precise measurement of the flux can probe the MikheyevSmirnov and Wolfenstein (MSW) effect of neutrino mixingas well as alternatemodels likeNon Standard Interactions [3]Another open question in the solar neutrino field is related tothe solar metallicity The Standard Solar Model was alwaysin excellent agreement with helioseismology until recentanalyses suggested a metallicity about 30 lower than the

Advances in High Energy Physics 3

previousmodelThis raised the question of the homogeneousdistribution of elements heavier than helium in the Sun Themeasurement of theCNOneutrino flux could be used to solvethe problem [4]

This paper is structured as follows In Sections 2 and 3 theSNO+ experiment is described including the current statusand detector upgradesThe expected background sources arepresented in Section 4 In Sections 5 to 9 the broad physicsprogram of SNO+ is described the neutrinoless double-betadecay search (Section 5) the measurement of low energysolar neutrinos (Section 6) the measurements of geo andreactor antineutrinos (Section 7) the supernova neutrinowatch (Section 8) and the exotic physics searches (Section 9)A brief conclusion follows at the end

2 The SNO+ Experiment

The SNO+ experiment [5] is located in the undergroundlaboratory of SNOLAB Sudbury Canada A flat overburdenof 2092m of rock provides an efficient shield against cosmicmuons corresponding to 5890 plusmn 94mwe [6] The resultingmuon rate through a 83m radius circular area is 63 muonsper day SNO+willmake use of the SNOdetector structure [78] consisting of a spherical acrylic vessel (AV) of 6m radiusand 55 cm thickness located within a cavity excavated in therock The vessel will be filled with about 780 tonnes of liquidscintillator and will be viewed by sim9300 PMTs supported bya geodesic stainless steel structure (PSUP) of approximately89m radius The volume between the AV and the PSUP aswell as the rest of the cavity will be filled with about 7000tonnes of ultra-pure water which acts as a shield for theradioactivity coming from the rock (cavity walls) and thePMT array A system of hold-up ropes suspends the acrylicvessel inside the PSUP Additionally in order to balance thebuoyant force due to the lower density of the liquid scintillatorcompared to the external water a new system of hold-downropes has been installed on the top part of the AV andanchored at the cavity floor A sketch of the detector is shownin Figure 1

Themajor detector upgrades including the liquid scintil-lator process systems are described here

21 Liquid Scintillator The SNO+ liquid scintillator (LS) iscomposed of an aromatic hydrocarbon linear alkylbenzene(LAB) as a solvent and a concentration of 2 gL 25-diphenyloxazole (PPO) as a fluor LAB was selected as theliquid scintillator for SNO+ because of (1) its long timestability (2) compatibility with the acrylic (3) high puritylevels directly from the manufacturer (4) long attenuationand scattering length (5) high light yield and (6) linearresponse in energy Additionally it has a high flash pointand is environmentally safe LAB will be produced very closeto the detector location (at the Cepsa plant in BecancourQuebec less than 900 km away) allowing short transporttimes which are important to reduce the possibility ofcosmogenic activation

22 Te-Loading One of the main advantages of using LABas liquid scintillator is the possibility of dissolving heavy

Figure 1 The SNO+ detector figure from [9] The 12m diameteracrylic vessel (blue) is viewed by sim9300 PMTs supported by a sim18mdiameter geodesic structure (green) and is held by a system of highpurity ropes (purple) The AV and the PSUP are within a volumeof highly purified water A rope net (red) will be used to offset thebuoyancy of the liquid scintillator contained within the AV

metals with long term stability and good optical propertiesFor the 0]120573120573-decay phase of the experiment SNO+ will loadtellurium into the liquid scintillator An innovative techniquehas been developed to load tellurium at concentration levelsof several percent into LAB maintaining good optical prop-erties and reasonably high light emission levels [10] Telluricacid Te(OH)

6 is first dissolved in water and then adding a

surfactant loaded into the scintillator To better match thePMT quantum efficiency a secondary wavelength shifter willalso be added to the mixture Currently we are investigatingtwo different secondary wavelength shifters perylene andbis-MSB The former shifts the emission peakrsquos range from350ndash380 nm to sim450ndash480 nm with a predicted light yield inSNO+ of about 300Nhits (detected photoelectron hits) perMeV of energy The latter shifts the emission peak to sim390ndash430 nm with a light yield of 200NhitsMeV The final choicewill depend on the timing optical properties the light yieldand the scattering length of the full scintillator mixture

23 Emission Timing Profiles and Optical Properties Theemission timing profile and the optical properties of theLAB-PPO and the Te-loaded scintillator have been thor-oughly investigated The timing profile of scintillation pulsesdepends on the ionization density of the charged particleswith signals caused by electrons being faster than thosefrom protons or alpha particles This property allows thediscrimination among particle types which is very importantfor background rejection The timing profile of electron andalpha particles in the unloaded scintillator has beenmeasuredin [11] Results show that for a LAB-PPO sample a peak-to-total ratio analysis allows us to reject gt999 of the alphaparticles while retaining gt999 of the electron signal


The measurement of the timing profiles in the 03 Te-loaded scintillator is described in [12] The presence of waterand the surfactant in the cocktail reduces the long tail of thealpha decay (slow component) with respect to the unloadedscintillator resulting in a poorer discrimination between 120572-like and 120573-like signals The light yield of the unloaded LAB-PPO scintillator has been measured in bench top tests andextrapolated for the full SNO+ volume using Monte Carlo(MC) simulations leading to 520NhitsMeV

The energy response to the electron energy depositionthe index of refraction and the absorption length of theLAB-PPO liquid scintillator are investigated in [13 14] Theenergy response is linear in the region from 04MeV to30MeV while below 04MeV the linearity is lost due toreemission effects and the loss of Cherenkov light (thresholdof sim02MeV)

Finally the quenching of proton and alpha particles forthe unloaded scintillator and the Te-loaded cocktail hasbeen measured in [15 16] The nonlinear energy-dependentprotonalpha light output is typically parametrized by Birksrsquoparameter 119896119861 [17] Its measurement is extremely importantfor the development of background rejection techniques asdescribed in Section 4 For protons in the unloaded SNO+scintillator the value measured in [15] is 119896119861 = 00098 plusmn00003 cmsdotMeVminus1 The measured value for alpha particles is119896119861 = 00076 plusmn 00003 cmsdotMeVminus1 corresponding approxi-mately to a quenching factor of 10 for energies between 5MeVand 9MeV

24 Process Plant The scintillator purification plant of SNO+is fully described in [18 19] It will use the same techniquesand has the same cleanliness requirements as the Borexinoexperiment by which we expect to reach a purity level ofabout 10minus17 ggLAB for both the 238U and 232Th chain [20]corresponding to 9 counts per day (cpd) for the 238U chainand 3 cpd for the 232Thchain Similar background levels havealso been achieved by the KamLAND experiment [21] Amultistage distillation (to remove heavy metals and opticalimpurities) and a high temperature flash vacuum distillationare initially used to separately purify LAB and PPOThen thePPO is combined with the LAB and the scintillator is furtherpurified by a N

2steam gas stripping process to remove gases

such as Rn Ar Kr O2 and residual water

After the detector fill the entire scintillator volume canbe recirculated in about 4 days to enable quasi-batch repu-rification and ex situ radio-assaying A rotating-stage liquid-liquid extraction column (water-LAB) and metal scavengersare used to effectively remove metals (K Pb Bi Th and Ra)Finally microfiltration is used for removal of suspended fineparticles

During the neutrinoless double-beta decay phase thetellurium the water and the surfactant will be purified priorto addition to the LAB-PPO scintillator The purificationtechnique for tellurium is described in [22] It has beendesigned to remove both the U- andTh-chain impurities andthe isotopes produced by cosmogenic neutron and protonspallation reactions while handling and storing telluriumon surface It consists of a double-pass acid-recrystallization

Figure 2 Sketch of the hold-down rope system on the top ofthe acrylic vessel to compensate for the buoyant force that thescintillator produces on the AV

on the Earthrsquos surface for which the overall purificationfactor reached in UTh and cosmogenic-induced isotopes isgt104 Since the tellurium purification is expected to happenat the above ground facilities and some isotopes can becosmogenically replenished evenwith short time exposures asecondpurification stage is neededunderground In this stagetelluric acid is dissolved in water at 80∘C and left to cool torecrystallize without further rinsing A further purification ofabout a factor 100 is obtained Currently we are investigatingthe possibility of moving the above ground purificationunderground in order to reduce potential recontamination

Thewater purification plant at the SNOLABundergroundlaboratory is based on the SNO light water purification plantwhich has been upgraded to improve its performance

Spike tests have shown that some of the isotopes producedby cosmogenic activation of the surfactant are harder toremove by purification than in the case of telluric acid Theprocedure to obtain pure surfactant will therefore be basedon its chemical synthesis in a dedicated underground plant

25 AVRope System TheSNO+ liquid scintillator has a lowerdensity (120588 = 086 gcm3 for LAB-PPOat119879 = 12∘C) comparedto the surrounding light water requiring a new hold-downrope system (see Figure 2) to compensate the buoyant forceanchoring the acrylic vessel to the cavity floor The newhold-down rope system consists of very high purity high-performance polyethylene fiber (Tensylon) ropes of 38mmdiameter The original hold-up rope system has also beenreplacedwith newTensylon ropes of 19mmdiameter in orderto reduce the radioactivity contamination

26 PMTs and Electronics SNO+ uses the original 8 inchSNO photomultiplier tubes (Hamamatsu R1408) Each PMTis equipped with a 27 cm diameter concentrator increasingthe effective photocathode coverage to about 54 FaultyPMT bases have been repaired and replaced and about9400 PMTs (90 of which are facing outwards) are expected


Table 1 Calibration sources that are considered for use by the SNO+ experiment

Source AmBe 60Co 57Co 24Na 48Sc 16N 220Rn222RnRadiation n 120574 120574 120574 120574 120574 120574 120572 120573 120574

Energy [MeV] 22 44 (120574) 25 (sum) 0122 41 (sum) 33 (sum) 61 Various

to be in operation at the start of the SNO+ experiment datataking

In SNO+ the use of liquid scintillator as target volumegreatly increases the light yield in contrast to the SNOheavy water allowing the measurement of very low energysignals like pp solar neutrinos (04MeV end-point energy)Moreover some of the background event types have highrates of several hundredHz For these reasons the SNO read-out boards and the data acquisition system were replacedwith new ones capable of a higher bandwidth New utilitieshave been added to the SNO+ trigger systemwhich will allowfor a more sophisticated use a flexible calibration interfaceand new background cuts to improve the physics sensitivityThe SNO+ trigger window is 400 ns long during which timeinformation and charge are collected from every PMT thatfired A dead-time of 30ndash50 ns separates two trigger windows[9]

In 2012 and 2014 the new electronics and trigger systemwere tested in runs with the detector empty and nearly half-filled with ultra-pure water (UPW)

27 Cover Gas System As long-lived radon daughters area potential background for the physics goals of SNO+ (seeSection 4) the original SNO cover gas system has beenupgraded to prevent radon ingress in the detector duringoperation It consists of a sealed system filled with high puritynitrogen gas which acts as a physical barrier between thedetector and the sim130 Bqm3 of radon in the laboratory airA new system of radon tight buffer bags has been designedand installed to accommodate the mine air pressure changeswith the aim of reaching a factor 105 in radon reduction

28 Calibration Systems The SNO+ detector will be cali-brated using both optical sources (LEDs and lasers coupled tooptical fibers) and radioactive sources (beta gamma alphaand neutron) The optical sources are used to verify thePMT response and to measure in situ the optical propertiesof the detector media while the radioactive sources areused to check the energy scale the energy resolution thelinearity of the response and the detector asymmetries andto determine the systematic uncertainties and the efficiencyof all reconstructed quantities (ie energy position anddirection) Additionally a system of cameras in underwaterenclosures will be used to monitor the position of the acrylicvessel and the hold-down rope system and to triangulate thepositions of the calibration sources inserted into the detector

The SNO+ calibration hardware has been designed tomatch the purity requirements of SNO+ and the need to havematerials compatible with LAB The calibration sources willbe attached to an umbilical and moved by a system of highpurity ropes in order to scan the detector off the central axisin two orthogonal planes

The set of radioactive sources that are considered forthe SNO+ experiment is shown in Table 1 covering theenergy range from 01MeV to 6MeV In addition the internalradioactivity can be used to calibrate the detector and checkany energy shift or variation of the response during data tak-ing Typical calibration references are 210Po-alpha 14C-betadelayed 214Bi-Po (238U chain) and 212Bi-Po (232Th chain)coincidences and muon followers

The optical calibration hardware consists of internallydeployable sourcesmdasha laserball (light diffusing sphere) anda Cherenkov source for absolute efficiency measurementsmdashand an external system consisting of sets of optical fibersattached to the PSUP in fixed positions sending pulses fromfast LEDs or lasers into the detector This system allowsfrequent calibrations of the PMTs response time and gain[23] and measuring the scattering and attenuation length ofthe scintillator without the need for source insertion

29 Simulation and Analysis AGeant4-based software pack-age RAT (RAT is an Analysis Tool) has been developed tosimulate the physics events in the SNO+ detector in greatdetail and to perform analyses such as vertex reconstruc-tion The RAT simulation includes full photon propagationfrom generation via scintillation and Cherenkov processesthrough to absorption and detection on the PMTs Thedetailed data acquisition and trigger systems are also partof the simulation Several particle generators have beendeveloped to simulate 0]120573120573-decay events solar neutrinosgeoneutrinos reactor antineutrinos supernova neutrinosand antineutrinos The decay schemes of all relevant back-ground isotopes are also part of the simulation tool RATcommunicates with a database that contains calibrationconstants and parameters describing the detector statusduring each run This includes the optical properties ofthe various components of the scintillator cocktail PMTcalibration constants and detector settings such as channelthresholds Algorithms have been developed to reconstructevent information such as the vertex position event direction(where relevant) and deposited energyThe SNO+MC tool iscontinuously tuned to match newly available measurements

For all SNO+ physics topics we have run a full MonteCarlo simulation to predict the fraction of background eventsin the corresponding region of interest (ROI) fromwhich wehave evaluated our sensitivities

3 Physics Goals Current Status and Run Plan

The primary goal of SNO+ is to search for the neutrinolessdouble-beta decay of 130Te However it has the potential toexplore other physics including the following


(i) Low Energy pep and CNO Solar Neutrinos The pepneutrinos can be used to constrain new physics scenarioson how neutrinos couple to matter while the CNO-neutrinoflux can shed light on unresolved questions regarding solarmetallicity

(ii) Geoneutrinos They are produced by the decay of U andTh chains in the Earthrsquos crust and mantle They can help tounderstand the heat production mechanisms of the Earthitself

(iii) Reactor Antineutrinos These can be used to betterconstrain the Δ1198982

12

neutrino oscillation parameter

(iv) Supernova Neutrinos and Antineutrinos The ability todetect a galactic supernova provides the potential for improv-ing models of supernova explosions

(v) Exotic Physics The low background expected in SNO+allows searches for processes predicted by physics beyondthe standard model (other than 0]120573120573-decay) like invisiblenucleon decay and solar axion or axion-like particle searches

Currently the SNO+ cavity is partially filled with ultra-pure water The upgrades to the SNO+ detector are nearlycompleted with a few items to be finished before the start ofdata takingThedetector parts that need to be finalized are theinstallation of the calibration system underwater camerasand the calibration optical fibers in most of the positionsabove the SNO+ equator and the replacement of the PMTsThe installation will proceed along with the rise of the waterlevel in the cavity The scintillator plant is nearly completedThe newly installed electronic and trigger system and part ofthe optical calibration system have been tested in air and withthe partially water-filled detector

The data taking period of SNO+will be divided into threemain phases

Water Phase In this phase the acrylic vessel will be filledwith about 905 tonnes of ultra-pure water and data takingwill last for a few months The main physics goals will be asearch for exotic physics including solar axion-like particlesand invisible nucleon decay in 16O the watch for supernovaneutrinos and the detection (potentially) of reactor antineu-trinos During this phase the detector performance the PMTresponse and the data acquisition system characteristics willbe tested Optical calibrations to test the response of the PMTconcentrators and the attenuation of the external water andthe acrylic will be performedThe backgrounds coming fromexternal sources like external water PMT array hold-downropes and the acrylic vessel will be characterized

Pure Scintillator Phase In this phase the detector will befilled with about 780 tonnes of LAB-PPO liquid scintillatorand data taking will last for a few months The physicstopics covered are the measurement of the low energy solarneutrinos themeasurement of geo and reactor antineutrinosand the supernova neutrino watch This phase will also beused to verify the opticalmodel and the detector response andto characterize the backgrounds due to internal and externalradioactive sources

Te-Loading Phase This phase is foreseen to start in 2017 andlast for about 5 years In this phase also called Phase Iabout 23 tonnes of natural tellurium (03 loading byweight)will be added to the detector for the search for the 0]120573120573-decay of 130Te Simultaneously geo and reactor neutrinoscan be observed and the detector will be live to a potentialsupernova

The physics program and capabilities of SNO+ will bediscussed in Sections 5 to 9

4 Backgrounds

The background sources of the SNO+ experiment can bedivided into two main categories internal and externalInternal backgrounds are all the non-signal interactions thatoccur inside the AV (119877 lt 6m) External backgrounds are theinteractions that are produced in the region outside the targetvolume but that can propagate or are reconstructed within itFull Monte Carlo simulations along with ex situ assays areused to explore the different background sources and developrejection techniques

In the following subsections the various backgroundsources are presented internal 238U chain (Section 41) 210Biand 210Po decays (Section 42) internal 232Th chain (Sec-tion 43) internal 40K 39Ar and 85Kr decays (Section 44)cosmogenically induced isotopes (Section 45) (120572 n) reac-tions (Section 46) pile-up events (Section 47) and externalbackgrounds (Section 48)

41 Internal 238U Chain 238U (11987912

= 447times 109 yr) is a natu-rally occurring radioisotope present in the liquid scintillatorThe part of the decay chain relevant for SNO+ is shown inFigure 3The 238Udaughters ofmost concern are 214Bi 210Tland 210Bi (see Section 42) Secular equilibrium with thetop part of the chain is assumed through the paper unlessotherwise noted214Bi (119879

12= 199min) beta-decays to 214Po with a 119876-

value of 327MeV in 99979 of the cases This decay canbe tagged using the 214Po alpha decay (119879

12= 1643 120583s

119864120572= 77MeV) during both the pure scintillator and the Te-

loaded phase In the pure scintillator phase the 120573-120572 delayedcoincidence will be used to measure the concentration ofthe 238U-chain contaminants 214Bi is expected to be insecular equilibrium with the top part of the 238U chain formost of the data taking period This equilibrium can bebroken by radon ingress into the detector during calibrationcampaigns or from emanation by the calibration hardwarematerialsHowever for non-continuumsources of radon dueto the short half-life of 214Bi equilibrium will be restored ina few weeksrsquo time In SNO+ the presence of the cover gas onthe top of the detector provides an efficient barrier againstlaboratory air highly reducing the radon ingress into thedetector (see Section 27) Additionally most of the radonshort-lived daughters decay in the cover gas region or in thedetector neck thus they do not reach the fiducial volume

During the Te phase the delayed coincidence techniquewill be used to reject 214Bi events that fall into the region ofinterest (ROI) for the 0]120573120573-decay search


214Bi

210Bi

210Tl

206Pb

210Pb

210Po

214Po

Q-value = 562MeV

T12 = 13min

T12 = 199min

T12 = 501d

T12 = 222 yr

T12 = 1643120583s

T12 = 1384d

120572-decay120573-decay

gt99 120573-decay

Q-value = 548MeV

120573-decayQ-value = 006MeV


Q-value = 783MeV

Q-value = 327MeV


0021 120572-decay

Figure 3 Part of 238U-decay chain relevant for SNO+ with 119876-values (total kinetic energy released in the ground state-groundstate transition) half-life and decay modes [24] The red squareshighlight the nuclides of most concern 214Bi 210Tl and 210Bi Thedecays used for 120572-120573 and 120573-120572 coincidence techniques are shownwith a blue arrow (dash-dotted line)

Usually Bi-120573 and Po-120572 are separated bymore than 250 nsand the SNO+ detector records them as two separate eventsThe secondary events (alpha candidates) are identified byapplying an energy cut around the alpha energy shifteddue to quenching to sim08MeV electron equivalent energyand by the short time separation from the preceding eventTo reduce the misidentification of the events due to otherdecays occurring in the same energy region during thecoincidencewindow a position cut can also be applied An 120572-120573 classification algorithm has been developed to furtherreduce themisidentification by classifying the events as120572-likeor 120573-like based on the hit-time distribution

Occasionally the beta and the alpha decays are separatedby less than 250 ns and they may be recorded as a singleevent by the SNO+ detector These events are importantfor the 0]120573120573-decay phase as they may fall into the ROI Inthis case the rejection technique is based on the distortionin the time distribution of the light detected by the PMTscompared to the case of a single interaction This rejectiontechnique is enhanced if a pulse shape analysis can be appliedto distinguish beta from alpha events

In 0021 of the cases 214Bi alpha-decays to 210Tl (11987912

=

13min) which beta-decays to 210Pb with a 119876-value of55MeV Due to the small branching ratio this route is less

Table 2 Target levels in gg and corresponding decay rates for theinternal 238U- and 232Th-chain contaminants in the various SNO+phases Secular equilibrium has been assumed for all the isotopesexcept 210Pb 210Bi and 210Po The levels of 210Bi and 210Po duringthe pure scintillator phase and the Te-loaded phase are expectedto be out of secular equilibrium due to the intrinsic scintillatorcontamination and the leaching off of the AV surface For the 03Te-loaded scintillator the telluriumpolonium affinity component isalso included in the 210Po decaysyr (see text)

Source Target [gg] DecaysyrInternal H

2

O water phase238U chain 35 times 10minus14 12 times 107232Th chain 35 times 10minus15 41 times 105

LAB-PPO pure scintillator phase238U chain 16 times 10minus17 4900232Th chain 68 times 10minus18 700210Bi mdash 76 times 108

a

210Po mdash 78 times 108a

03 Te-loaded scintillator Te phase238U chain 25 times 10minus15 76 times 105232Th chain 28 times 10minus16 28 times 104210Bi mdash 79 times 109

b

210Po mdash 95 times 109b

aExpected number of events in the first year after 9 months of water phasebExpected number of events in the first year after 9 months of water phasefollowed by 6 months of pure scintillator phase

important than the previous one An 120572-120573 delayed coinci-dence similar to the 120573-120572 one can be applied However dueto the longer half-life of 210Tl the mistagging probability islarger with respect to the 214Bi-Po one which may result in alarger signal sacrifice

Based on Borexino Phase-I achievements [20] the puritylevel aimed (target level) in the LAB-PPO scintillator forthe 238U chain is 16 times 10minus17 gg (see Table 2) During the Te-loaded phase the addition of the isotope the water and thesurfactant to LAB will worsen the mixture purity but we willmaintain a strict target level of 25 times 10minus15 gg (see Table 2)

42 210Bi and 210Po Backgrounds The ingress of 222Rn intothe SNO+ detector can break the secular equilibrium inthe 238U chain at 210Pb (119879

12= 222 yr119876-value = 006MeV)

resulting in a higher concentration of this isotope Evenif 210Pb is not a direct background for the SNO+ experimentits daughters 210Bi (119879

12= 50 d 119876-value = 116MeV)

and 210Po (11987912

= 1384 d 119864120572

= 53MeV shifted to sim05MeV electron equivalent energy) are potentially relevantfor the various physics searches 210Bi-beta decays are themain background for the CNO-] measurement as they havesimilar spectral shapes while the 210Po-alpha decay is a back-ground for the 120573-120572 and 120572-120573 delayed coincidences resultingin mistagging and potential signal sacrifice Additionally theemitted alphas can interact with the atoms in the scintillatorproducing neutrons as described in Section 46 The covergas system placed at the top of the acrylic vessel greatly


reduces the radon ingress into the detector Furthermore themajority of short-lived daughters decay before reaching thefiducial volumeHowever due to its long half-life 210Pb is notattenuated by the presence of the detector neck and reachesthe target volume210Pb and its daughtersmay also leach frommaterials that

are in contact with the liquid scintillator Radon daughtersdeposited on the materialrsquos surface can implant by alpharecoil to a depth of a few hundred nm where they eventuallydecay to 210Pb 210Pb 210Bi and 210Po atoms might thenleach offwhen the liquid scintillatormixture is in contactwiththe surface This process can happen for instance duringthe handling and storing of the liquid scintillator resultingin rates of 210Pb 210Bi and 210Po out of equilibrium withthe 238U chain Concentrations of 210Bi and 210Po differentfrom each other and the rest of the 238U chain have beenseen by the Borexino experiment [25] The levels initiallymeasured by Borexino for these two isotopes are included inTable 2

An additional source of 210Pb 210Bi and 210Po is leach-ing from the internal surface of the AV where radondaughters have implanted during the construction of SNOand when the detector was empty after draining the heavywater This may create a continuous source of 210Pb 210Biand 210Po during the data taking period for all SNO+ phasesLeaching rates depend on several factors like temperatureimplantation depth type of liquid in contact with the surfaceand initial surface activity The leaching rate of 210Pb andits daughters for all the scintillator mixtures and the ultra-pure water at different temperatures have been measured inbench top tests With a measured activity of about 1 kBq onthe inner AV surface the activity of 210Pb daughters leachedin the scintillator media might be as high as a few hundredBq depending on the duration of the data taking periodThe activity of the backgrounds leached in the scintillator isexpected to increase with time while that of inner surfaceevents is expected to decrease

In the Te-loaded phase an additional source of 210Po isthe tellurium itselfTheCUOREcollaboration has shown [26]that due to the chemical affinity between tellurium and polo-nium this element may still be present in tellurium after thecrystal production process In our background estimationswe assume an additional 210Po activity of 006 BqkgTe basedon CUORE measurements These decays however are notsupported by 210Pb and are considerably reduced to about16 of the initial activity in a year after tellurium productionThis contribution is included in the purity levels of 210Poshown in Table 2

43 Internal 232Th Chain 232Th (11987912

= 14 times 1010 yr)is also a naturally occurring radioisotope present in theliquid scintillator The daughters of most concern are 212Biand 208Tl (see Figure 4)212Bi (119879

12= 606min) beta-decays to 212Po (119879

12=

300 ns) with a119876-value of 225MeV in 64 of the cases As forthe 214Birarr 214Po decay many events can be selected using a120573-120572 delayed coincidence which is used to extract the concen-tration of the 232Th-chain contaminants in equilibrium in the

212Bi

208Tl

208Pb

212Po

36 120572-decayQ-value = 621MeV

T12 = 31min

T12 = 606min

T12 = 0299120583s



Q-value = 500MeV Q-value = 895MeV

Figure 4 Part of 232Th-decay chain relevant for SNO+ with 119876-values half-life and decay modes [24] The red squares highlightthe most important nuclides 212Bi and 208Tl The decays used for120572-120573 and 120573-120572 coincidence techniques are shown with a blue arrow(dash-dotted line)

pure scintillator Nearly 45 of the 212Birarr 212Po decays fallin the same trigger window and are a potential backgroundfor the 0]120573120573-decay search These can be rejected using thePMT timing distribution

In the remaining 36 of the cases 212Bi alpha-decaysto 208Tl (119879

12= 30min) which beta-decays to 208Pb with

a 119876-value of 50MeV An 120572-120573 delayed coincidence can beapplied to identify the 208Tl events as for the 210Tl case

The LAB-PPO scintillator target level for the 232Thchainis 68times10minus18 gg (based on [20]) while the target level for theTe-loaded scintillator is 28 times 10minus16 gg (see Table 2)

44 Internal 40K 39Ar and 85Kr Backgrounds Other internalbackgrounds are important for solar neutrino and othermeasurements40K (119879

12= 1248 times 109 yr) has a very distinctive energy

spectrum having both a beta component and a gamma peakat 146MeV Due to the long half-life it is naturally present inthe scintillator and detector materials39Ar (119879

12= 269 yr) and 85Kr (119879

12= 108 yr) decay with

a 119876-value of 0565MeV and of 0687MeV respectively Theamount of these isotopes can be reduced by minimising thecontact time of LAB with air and thoroughly degassing thescintillator

45 Cosmogenically Induced Backgrounds Besides the nat-ural radioactivity present in the scintillator LAB can beactivated by cosmic ray neutrons and protons while it isabove ground The main expected background is 7Be (119879

12=

532 d EC-decay with a 048MeV gamma) with a maximumproduction rate at sea level (neutron and proton flux from[27 28]) of about 1 kHz for 780 t of liquid scintillator Morethan 99 of the produced 7Be can be efficiently removed bythe scintillator purification plant14C (119879

12= 5700 yr 119876-value = 016MeV) is naturally

present in the liquid scintillator It is a direct backgroundfor the very low energy pp neutrino measurements andmay contribute to pile-up backgrounds (see Section 47)In SNO+ we expect a 14C12C ratio of the order of 10minus18


similar to what was observed in the Borexino test facility [29]corresponding to a decay rate of a few hundred Hz This is areasonable assumption as in both cases the liquid scintillatoris obtained from old oil fields in which most of 14C hasdecayed away The amount of 14C produced by cosmogenicactivation of LAB during transport to site is negligible incomparison11C (119879

12= 20min 119876-value = 198MeV) is mainly

produced by muon interactions with the carbon nuclei ofthe liquid scintillator We expect a total of (114 plusmn 021) times103 decaysktyr during operation extrapolated from Kam-LAND data in [30] This is about a factor 100 less than whatwas observed in Borexino [31] due to the deeper undergroundlocation A threefold coincidence tagging technique like theone developed by Borexino [32] together with an electron-positron discrimination analysis [33] will further reducethese events

Other muon induced backgrounds are generally veryshort lived (milliseconds to seconds half-life) and can berejected by vetoing the detector for a few minutes after eachmuon event

Important cosmogenic-induced backgrounds are iso-topes produced by spallation reactions on tellurium while itis stored on surface [34] like 124Sb (119879

12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912

= 2498 d119876-value = 289MeV 119864parent(level) = 0118MeV) and 88Y(11987912

= 1066 d 119876-value = 362MeV) We have developeda purification technique [22] (see Section 24) that togetherwith underground storage reduces the cosmogenic-inducedbackground on tellurium to a negligible level

46 (120572 n) Backgrounds Neutrons can be produced in theliquid scintillator by (120572 n) reactions on 13C or 18O atomsmuon interactions in the scintillator volume 238U fissionand (120574 n) reactions for 119864

120574gt 3MeV Excluding the muon

induced neutrons the most prominent neutron source insidethe scintillator volume is the 120572 + 13Crarr 16O + n reaction(119864thr = 00 keV) which is a potential background for boththe 0]120573120573-decay search and the antineutrino measurementThe main source of alpha particles in the various scintillatormixtures is 210Po Other U- and Th-chainrsquos alpha emittersform a negligible contribution as they are expected to be sim4orders of magnitude less abundant

Neutrons produced in (120572 n) reactions will scatter fromprotons during the thermalization process resulting in recoilsemitting scintillation lightThe visible proton energy togetherwith the energy lost by the alphas before interaction isthe prompt signal If the isotope is in an excited state theemitted deexcitation gammas are also part of the promptsignal The thermalized neutrons in gt99 of the cases areeventually captured by hydrogen atoms with the emission ofthe characteristic 222MeV-120574 In the remaining sim1 of thecases the thermal neutron is captured either on telluriumisotopes producing mainly a 06MeV gamma or on 12Cproducing a 495MeV gamma The prompt and the delayedsignal can be used to reject the (120572 n) background using adelayed coincidence technique similar to that of 120573-120572 events

47 Pile-Up Backgrounds A pile-up event occurs when twoor more decays (signal or background or a mixture) happenin the same trigger window and thus are potentially detectedas a single event with energy equal to the sum of thesingle energies Pile-up events become important when theevent rate of one or all of the contributing decays is veryhigh (hundreds of Hz) like 14C decays or 210Bi or 210Po Arejection technique using the distortion of the timing is usedto efficiently reduce these backgrounds [35 36]

48 External Backgrounds Sources of external backgroundinclude the hold-down and hold-up ropes the PMT arraythe AV bulk and the external water (see Table 3) Radioactivedecays occur outside the scintillator volume so the mainconcerns for the signal extraction analysis are the highenergy gammas and betas emitted by 214Bi 208Tl and 40Kdecays External background events reconstructing inside theAV can be greatly reduced by applying a fiducial volumecut Events can be further reduced using the PMT timedistribution In situ analysis during the water phase andthe pure liquid scintillator phase will help to constrain theexternal backgrounds for the Te-loaded phase

5 130Te Neutrinoless Double-Beta Decay

Themain goal of the SNO+ experiment is the search for neu-trinoless double-beta decay of 130Te (119876-value = 2527518 plusmn0013 keV [40]) by loading large quantities of the isotopeinto the liquid scintillator volume This approach has severaladvantages (1) external backgrounds can be removed by fidu-cialization (2) internal and external background levels can bemeasured before and after the isotope deployment allowingidentification and removal of possible contamination (3)internal backgrounds can be tagged by coincidences orparticle identification (4) the detector response can be testedwith and without the isotope (5) the spatial distribution ofmost background isotopes in a liquid is known to be uniform(6) the loading can be easily and affordably scaled up or (7)changed to another isotope and (8) tellurium and scintillatorcan be removed and repurified if high levels of backgroundsare found

The choice of 130Te as the preferred 0]120573120573 candidateis the result of an extensive investigation by the SNO+collaboration The decision was based on several factorsincluding the following points

(1) 130Te has a large natural abundance of 3408 whichallows loading of several tonnes of isotope withoutenrichment

(2) The measured half-life of the 130Te 2]120573120573 decay is(70 plusmn 09 (stat) plusmn 11 (syst)) times 1020 yr [41] one of thelongest of all the 0]120573120573 isotopes This is particularlyimportant for liquid scintillator-based experimentsas the energy resolution is usually some hundreds ofkeV

(3) An innovative loading technique has been developedwhich enables deployment of up to 5 (by weight) of


Table 3 238U- and 232Th-chain levels for external background sources Shown are measured levels and expected decay rates

Source Measured levels Decaysyr

Internal ropes214Bi (28 plusmn 54) times 10minus10 gUg [37] 4966208Tl lt20 times 10minus10 gThg [37] lt418

Hold-down ropes214Bi (47 plusmn 32) times 10minus11 gUg [37] 406 times 106

208Tl (227 plusmn 113) times 10minus10 gThg [37] 232 times 106

Hold-up ropes214Bi (47 plusmn 32) times 10minus11 gUg [37] 834 times 105


Water shielding214Bi 21 times 10minus13 gUg [38] 132 times 108

208Tl 52 times 10minus14 gThg [38] 392 times 106

Acrylic vessel214Bi lt11 times 10minus12 gUg

a [7] 128 times 107

208Tl lt11 times 10minus12 gThga [7] 150 times 106

Acrylic vessel external dustb214Bi (11 plusmn 01) times 10minus6 gUg [39] 78 times 105


Acrylic vessel internal dust214Bi (11 plusmn 01) times 10minus6 gUg [39] 415 times 104


PMTs214Bi 100 times10minus6 gUPMT [7] 37 times 1011

208Tl 100 times10minus6 gThPMT [7] 44 times 1010

aAssumed 10 times 10minus12 ggbIt is assumed that the top hemisphere of the external AV surface is not cleaned while the bottom hemisphere is at target level

Futurephase

1st phase(now)

03 05 1 3 5

Figure 5 TeLS samples from the investigation of higher telluriumloading in LAB scintillator The samples increase in loading from03 (by weight) on the left to 5 on the right

natural tellurium while maintaining good light trans-mission minimal scattering and an acceptable lightyield (see Section 22) The 03 tellurium scintillatorcocktail (TeLS) has been proven to be stable for aperiod of over two years In Figure 5 various SNO+loaded cocktails are shown Cocktails with higherloading still maintain good optical transparency

(4) TheTeLS does not present inherent optical absorptionlines in the visible wavelength range such that asecondary wavelength shifter may be added to thecocktail to better match the SNO+ PMT response

51 Backgrounds For the 130Te 0]120573120573 search an asymmet-ric region of interest (ROI) is defined which extendsfrom minus05120590 to 15120590 around theGaussian signal peak For the03 Te-loaded cocktail with a light yield of 200NhitsMeV(see Section 22) the energy resolution at 25MeV is sim270 keV(FWHM) while the averaged position resolution at the sameenergy is sim15 cm at the detectorrsquos center An asymmetric ROI

retains most of the 0]120573120573 decays but considerably reduces thebackgrounds from 2]120573120573 and low energy 238U- and 232Th-chain decays Most external backgrounds are rejected bya 35m fiducial radius cut which preserves 20 of signalevents Inside the 35m fiducial volume (FV) and 247MeVto 270MeV energy ROI the main background sources are asfollows

8B Solar Neutrinos Flat continuum background from theelastically scattered (ES) electrons normalized using thetotal 8B flux and published solar mixing parameters [42]

2]120573120573 Irreducible background due to the 2]120573120573 decaysof 130Te these events appear in the ROI due to the energyresolution of SNO+

External Backgrounds 208Tl and 214Bi nuclides contained inthe AV hold-down rope system water shielding and PMTglass are the major contributors in the defined ROI The FVcut of 20 reduces these background events by several ordersof magnitudeThe PMT hit-time distribution cut reduces theexternal background events falling in the FV by an additionalfactor of two

Internal 238U- and 232Th-Chain Backgrounds The dominantbackgrounds in the signal ROI are due to 214Bi-Po and 212Bi-Po decays Currently we have achieved approximately100 rejection of separately triggered 214Bi-Po and 212Bi-Podecays falling inside the ROI and FV using the 120573-120572 delayedcoincidence For 212Bi-Po and 214Bi-Po pile-up decays cutsbased on PMT hit timing achieve a rejection factor of sim50 forevents that fall in the ROI and FV Other minor contributionsin the ROI are due to 234mPa (238U chain) 210Tl (238U chain)and 208Tl (232Th chain)


Table 4 Expected background counts in the signal ROI and35mFV in SNO+ for the first year (year 1) and in 5 years of the 03Te-loading phase A light yield of 200NhitsMeV has been assumedCuts have been applied as described in the text

Isotope 1 year 5 years2]120573120573 63 3168B ] ES 73 363Uranium chain 21 104Thorium chain 17 87External 36 181(120572 n) 01 08Cosmogenics 07 08Total 218 1068

Cosmogenic Backgrounds The most relevant isotopes are60Co 110mAg 88Y and 22Na (see Section 45) The devel-oped purification techniques together with a long period ofunderground storage will reduce the cosmogenically inducedbackground to less than one event per year in the FV andROI

(120572 n) Backgrounds Both the prompt signal and the delayed222MeV-120574 produced by (120572 n) reactions can leak into the0]120573120573 ROI Coincidence-based cuts have been developed thatremovemore than 996 of the prompt and sim90 of delayedevents that fall in the FV and ROI

Pile-Up Backgrounds The most important pile-up back-grounds for 0]120573120573 search are due to high-rate 210Po +2]120573120573 and 210Bi + 2]120573120573 with bismuth and polonium comingfrom both the TeLS and the vessel surface Timing-based cutshave been developed that reduce the pile-up backgrounds toa negligible level

We have estimated the fraction of each background thatfalls in the ROI and FV based on our Monte Carlo simula-tions A summary of the various background sources in theROI and FV is shown in Table 4 The main contributions aredue to 8B ] ES and to 2]120573120573 A total of about 22 eventsyrin the FV and ROI are expected The scale of the externalbackground events within the ROI can be checked by fittingevents outside the fiducial volume Internal U- andTh-chainresiduals can be checked via the 214Bi-Po and the 212Bi-Podelayed coincidences whose tagging efficiency can be testedduring the pure LAB-PPO scintillator phase In additionsome of the cosmogenic-induced backgrounds like 124Sband 88Y can be constrained using their relatively short half-life while 8B-] and 2]120573120573 decays can be constrained by theirknown value Furthermore the detector response will betested through a detailed calibration (see Section 28)

The expected signal and background spectrum for a five-year live-time is shown in Figure 6 for the 03 loadingA fiducial volume cut is applied at 35m gt9999 rejectionfor 214Bi-Po and gt98 for 212Bi-Po are assumed and thelight yield is 200NhitsMeV The 0]120573120573 signal shown is for119898120573120573

= 200meV which corresponds to 1198790]12057312057312

sim 1 times 1025 yrusing the IBM-2 nuclear matrix element [43]

0120573120573 (200meV)2120573120573

U chainTh chain(120572 n)

External8B ESCosmogenicResiduals

23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV

Figure 6 Summary stacked plot of all backgrounds and a hypotheti-cal 0]120573120573 signal corresponding to a mass 119898

120573120573

= 200meV for 5-yeardata taking Events are shown in the FV of 35m for 03 naturaltellurium loading and 200NhitsMeV light yield 119879

120573120573

is the effectivekinetic energy

52 Sensitivity The expected number of 0]120573120573 events occur-ring in the SNO+ detector is given by

119878 = 120598 sdot 119873130

sdot ln 2 sdot 119905

1198790]12057312057312

(1)

where 120598 is the signal detection efficiency119873130

is the numberof 130Te atoms in the detector 119905 is the live-time and 1198790]120573120573

12

isthe half-life of 130Te 0]120573120573 To compute the SNO+ sensitivitywe assume that the number of observed events in the FVand ROI is equal to the expected backgrounds In this casethe numerical value of the derived bound on the number ofsignal events is similar for either a Bayesian or a frequentistdefinition of 90 confidence levelWith the natural telluriumconcentration of 03 (by weight) in Phase I correspondingto about 800 kg of 130Te a 20 FV cut and five years of datataking SNO+ can set a lower limit on the half-life of 1198790]120573120573

12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312

gt 48 times 1025 yr at 3120590 level)This corresponds to a limit on the effectiveMajorana neutrinomass 119898

120573120573 of 55ndash133meV using a phase space factor 119866 =

369 times 10minus14 yrminus1 [44] and 119892A = 1269 the range is due todifferences in nuclear matrix element calculation methods[43 45ndash48]


53 Higher Tellurium Concentration in the Future One of themain advantages of the SNO+ technique is the possibility ofmoving toward higher sensitivities by increasing the loadingRampD efforts have demonstrated that with 3 (by weight)tellurium loading a light yield of 150NhitsMeV can beachieved using perylene as a secondary wavelength shifterIn SNO+ Phase II this loss in light yield will be compen-sated by an upgrade to high quantum efficiency PMTs andimprovements to PMT concentrators These improvementswill increase the light yield by a factor of sim3 A preliminarystudy shows that SNO+ Phase II can set a lower limit on the0]120573120573 half-life of 1198790]120573120573

12

gt 7 times 1026 years (90CL) for a119898120573120573

range of 19ndash46meV

6 Solar Neutrino Physics

SNO+ has the opportunity to measure low energy solarneutrinos with unprecedented sensitivity This is due tothe reduced production rate of cosmogenic isotopes at theSNOLAB depth and requires that the intrinsic backgroundsources are low enough

At scintillator purity levels similar to that of BorexinoPhase I [20 25] the unloaded scintillator phase of SNO+provides excellent sensitivity to CNO pep and low energy 8Bneutrinos With the scintillator sourced from a supply lowin 14C SNO+ could also measure pp neutrinos with a sen-sitivity of a few percent Due to the relatively high end-pointof the spectrum 8B ]s with energy above the 130Te end-pointcan also be measured during the 0]120573120573-decay phase

The first measurement of the flux of neutrinos fromthe subdominant CNO fusion cycle would constrain themetallicity of the solar interior and thus provide criticalinput to the so-called solar metallicity problem the currentdisagreement between helioseismological observations of thespeed of sound and model predictions due to uncertaintiesin the heavy element (metal) content of the Sun Historicallymodel predictions for the speed of sound were in excellentagreement with observation one of the primary reasonsfor confidence in the Standard Solar Model during theperiod of uncertainty surrounding the solar neutrino prob-lem However recent improvements in solar atmosphericmodeling including transitioning from one-dimensional tofully three-dimensional models and including effects suchas stratification and inhomogeneities [49] produced a lowervalue for the heavy element abundance of the photosphereand thus changed the prediction for the speed of soundThe theoretical prediction for the CNO flux depends linearlyon the core metallicity and can be further constrained by aprecision measurement of the 8B flux due to their similardependence on environmental factors A measurement ofCNO neutrinos would thus resolve this uncertainty and alsoadvance our understanding of heavier mass main-sequencestars in which the CNO cycle dominates over the pp fusionchain

Precision measurements of the pep flux and the lowenergy 8B spectrum offer a unique opportunity to probethe interaction of neutrinos with matter and to search fornew physics The shape of the ]

119890survival probability in

the transition region between vacuum oscillation (le1MeV)and matter-enhanced oscillation (ge5MeV) is particularlysensitive to new physics effects such as flavor changingneutral currents or mass-varying neutrinos due to theresonant nature of the MSW interaction The pep neutrinosare a line source at 144MeV thus offering the potentialfor a direct disappearance measurement partway into thisvacuum-matter transition region However due to theirproduction region closer to the core of the Sun the effectof new physics on the 8B neutrino spectrum is significantlymore pronouncedThus the most powerful search combinesa precision measurement of the pep flux with a 8B spectralmeasurement

Borexino has published the first evidence for pep neu-trinos [33] with a significance of just over 2120590 from zeroIn order to distinguish different models a precision ofat least 10 is required A number of experiments haveextracted the 8B spectrum [42 50ndash53] and there is someweak evidence for nonstandard behaviour in the combineddata set [54] but the significance is low (roughly 2120590) Thetheoretical uncertainty on pep neutrinos is very small andwell constrained by solar luminosity measurements The 8Bflux is well measured by the SNO experiment [42] Preciseoscillation measurements are therefore possible

Should the SNO+ scintillator be sourced from a sup-ply naturally low in 14C similar to or within an order ofmagnitude or so of the level observed in Borexino therealso exists the potential for a precision measurement of ppneutrinos Borexino has produced the first direct detectionof these neutrinos with a precision of a little over 10 [55] Apercent level measurement would allow a test of the so-calledluminosity constraint thus testing for additional energy lossor generation mechanisms in the Sun and allowing us tomonitor the Sunrsquos output using neutrinos

61 Backgrounds Thesensitivity of the SNO+ solar phasewilldepend critically on the leaching rate of 210Bi As described inSection 42 radon daughters implanted on the internal AVsurface are expected to leach off during the various SNO+phases with a rate that depends both on the temperatureand on the liquid in contact with the vessel We will beable to evaluate the levels of these backgrounds both duringthe initial water fill and during the scintillator fill itself Weare also investigating mitigation techniques to be applied incase the background levels are initially too high to performthe solar measurement These techniques include in siturecirculation further purification and the use of a balloonto shield from external backgrounds

Other backgrounds for the measurements of pep andCNO neutrinos are the levels of 214Bi (238U chain) 212Bi(232Thchain) and 11C in the pure scintillator 238Uand 232Thlevels in the scintillator can be effectively constrained usingthe 120573-120572 delayed coincidence as described in Section 4 11Cdecays which were the main background for the measure-ment of pep neutrinos in Borexino [32] can be identified bya threefold coincidence algorithm (see Section 45)

Another muon induced isotope that is a potentialbackground for low energy 8B neutrino searches is 10C


(11987912

= 193 s 119876-value = 365MeV) However due to theisotopersquos short half-life and the low cosmic muon rate atSNOLAB depth it can be removed by cutting events thatoccur within a few minutes from each muon event

62 Sensitivity Sensitivity studies were performed assumingone year of unloaded scintillator data which could be eitherprior to or following the Te-loaded phase An extendedmaximum likelihood fit was performed in energy witha conservative 50 fiducial volume in order to reduceexternal background contributions to negligible levels Atwo-dimensional fit would allow an increase in fiducialvolume and thus improve sensitivity Thirty-four signalswere included in the fit the four neutrino signals (8B 7BeCNO and pep) as well as thirty background event typesBackgrounds expected to be in equilibrium were constrainedto a single fit parameter 210Po 210Pb and 210Bi were treatedindependently that is not assumed to be in equilibrium withthe parent decays Background parameters included in the fitwere the normalisations of 7Be 39Ar 40K 85Kr 210Po 210Pb14C 238U chain and 232Th chain 210Bi was linked to CNOin the fit due to the similarity of the energy spectra theseparation is best achieved by imposing an ex situ constrainton the level of 210Bi decays or by using observables other thanenergy

The nominal background levels assumed were thoseachieved by Borexino during their initial running It wasassumed that purification techniques (in particular distil-lation) can reduce 7Be contamination to negligible levelsGaussian constraints were applied to backgrounds where anex situ or independent in situ measurement of the rate isanticipated 120572 tagging is expected to reduce the 210Po peak by95 with an uncertainty of 20 on the remaining 5 of theevents Coincidence decays provide a 50 constraint on 85Kr25 on the 232Th-chain backgrounds and 7 on the portionof the 238U chain that is treated as being in equilibrium

The fit range was between 02MeV and 65MeV with10 keV bins in visible energy Extending the fit to higher ener-gies would improve the accuracy on the 8BfluxmeasurementBias and pull tests show that the fit is stable and accurateand robust to changes in bin size or energy range (to withinchanges in statistics eg 8B flux accuracy is reduced if theenergy range of the fit is reduced)

The simulations suggest that with one year of datathe uncertainty on the pep flux will be less than 10 Theuncertainty on the linkedCNO+ 210Bi flux is 45 intowhichwe fold a conservative uncertainty for separating the twosignals resulting in a 15 predicted uncertainty on the CNOflux The 7Be flux can be measured to 4 and 8B to betterthan 8The uncertainty on the neutrino flux measurementsis dominated by statistics and by correlations between theneutrino signals themselves A study of energy scale and reso-lution systematics shows that these parameters can be floatedas nuisance parameters in the fit and the data will constrainthem to better than the required precision with subpercentlevel impact on the neutrino flux uncertainties Calibrationsources will be deployed in order to measure effects such

Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep

Th chain39Ar210BiU chain11C85Kr210Po

Even

ts002

MeV

yea

rFigure 7 Expected solar neutrino fluxes as detected by SNO+and the corresponding main backgrounds Backgrounds levels areassumed to be equal to those initially achieved by Borexino [2025] (see text) Events are shown for the LAB-PPO scintillator400NhitsMeV light yield and a fiducial volume cut of 55m A95 reduction is applied to the 214Bi-Po backgrounds via delayedcoincidence tagging and a 95 reduction on the 210Po and theremaining 214Po events via alpha tagging

as any non-Gaussianity of the resolution function and anypotential nonlinearity in the energy scale In Figure 7 thefull solar neutrino signals as detected by SNO+ are showntogether with themain background sources for the LAB-PPOscintillator A fiducial volume cut is applied at 55m214Bi-214Po events are reduced by 95 using the 120573-

120572 delayed coincidence as described in Section 41 A 95rejection is applied to the 210Po events and the remaining214Po events via alpha tagging There is no rejection appliedto the 212Bi and 212Po events This is a conservative approachas we expect to reject the majority of these events using a 120573-120572 delayed coincidence as for the 0]120573120573 search (see Section 5)

Studies show that the precision with which the ppneutrinos could be observed depends critically on the levelsof backgrounds such as 14C and 85Kr in the scintillator Ifthese backgrounds are low within 10ndash50 times that seen inBorexino SNO+ could achieve a few-percent level measure-ment of the pp neutrino flux with just 6 months of solarneutrino data

7 Antineutrino Studies

Antineutrino events in SNO+ will include geoneutrinosfrom the Earthrsquos radioactive chains of uranium and thoriumantineutrinos from nuclear reactors and the antineutrinosemitted by a supernova burst (which are considered indetail in Section 8) The measurement of geoneutrinos will


constrain the radiogenic heat flow of the Earth for geophysicsstudies while themeasurement of reactor antineutrinos witha known energy spectrum and a precise propagation distancecan better constrain the neutrino oscillation parameters [56]

71 Signal Detection Antineutrinos are detected in SNO+via inverse beta decay (IBD) ]

119890s with energy greater than

18MeV interact with the protons in the liquid scintillatorproducing a positron and a neutronThe antineutrino energyis measured by the scintillation light emitted by the positronas it slows down and annihilates

119864]119890

≃ 119864prompt + (119872n minus119872p) minus 119898e

≃ 119864prompt + 08MeV(2)

where 119872n 119872p and 119898e are the neutron proton and elec-tron masses The neutron emitted in the reaction will firstthermalize and then be captured by hydrogen leading to thecharacteristic 222MeV delayed gamma from the deuteriumformationThe prompt + delayed signal allows the identifica-tion of the antineutrino event The coincidence time intervalis defined by the period elapsed from neutron emission to itscapture generally about 200120583s while the spatial separationbetween the prompt and the delayed event depends on thedistance travelled by the delayed gamma before scintillationlight is emitted The exact values to use for the time anddistance coincidence tag to identify the ]

119890events depend

crucially on the correct simulation of the neutron propa-gation in the scintillator mixture being used (unloaded orTe-loaded scintillator) Neutron propagation in each of thescintillator cocktails planned by SNO+ will be checked witha detailed calibration program using an AmBe source Thissource already extensively used by SNO has a well-knownneutron energy spectrum extending to energies higher thanthose of the expected antineutrino signals The calibrationresults will be cross-checked with a detailed Monte Carlosimulation

72 Backgrounds As the antineutrino signal is identifiedas a delayed coincidence in SNO+ the main backgroundsare true or random coincidences in the detector with theidentified neutron capture Most of the background neutronsare expected to come from external background sourcesand are therefore captured and reconstructed in the externalregions of the detector Events that reach the region insidethe vessel can be mitigated by a fiducial volume cut or bya radius-dependent analysis The major source of neutronsinside the scintillator is the (120572 n) reactions which are mainlycaused by 210Po-alpha leached off the vessel surface and areexpected to increase with time as described in Section 46The associated prompt signalmainly due to the proton recoilwill be at energies lower than 35MeV or in case the productnucleus is in an excited state in definite gamma peaks whichwill allow the study of the (120572 n) backgroundrsquos time evolution

73 Reactor Antineutrinos and Oscillations In SNO+ weexpect around 90 reactor antineutrino events per year Thetotal flux is obtained summing 3 components (1) 40 of it

1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)

Figure 8 Expected visible antineutrino energy spectrum in SNO+for 1032 proton-years per MeV The nonoscillated reactor spectrum(dashed line) is shown together with the geoneutrino spectrum(solid line arbitrary normalisation) The stacked oscillated reactorspectrum is shown with different colors each corresponding to areactor complex reactor at 240 km in blue (top) reactors at 350 kmin red (middle) and other reactors in yellow (bottom) See text fordetails

comes from one reactor complex in Canada at a baseline of240 km (2) 20 is from two other complexes at baselines ofaround 350 km and (3) 40 is divided between reactors inthe USA and elsewhere at longer baselines The signals fromthe first two sources (1 and 2) induce a very clear oscillationpattern (see Figure 8) which lead to a high sensitivity tothe Δ1198982

12

neutrino oscillation parameter For 119864 lt 35MeVthe geoneutrino signals and reactor signals overlap Most ofthe backgrounds are concentrated in the energy region of thegeoneutrinos For a preliminary study of the reactor neutrinooscillation sensitivity we conservatively exclude the regionbelow 35MeV Assuming a light yield of 300NhitsMeVexpected for the Te-loaded phase with perylene as secondarywavelength shifter and a 55m FV cut we expect to reacha sensitivity in Δ1198982

12

of 02 times 10minus5 eV2 similar to the Kam-LAND result [56] in about 7 years of data taking Thefull analysis will take the complete antineutrino spectruminto account using constraints for the backgrounds andmeasuring simultaneously the geoneutrino flux

Generally the ]119890flux from the Canadian reactors

(CANDU-type) is expected to be stable in time due to thecontinuous refuelling process However in the next few yearsthere are expected upgrades in which different reactor coreswill be turned off with only one reactor core switched off ata time in each of the complexes This will cause changes inthe reactor spectrum with an expected total flux reductionbelow 10 at each moment This time evolution can beused to identify the very clear oscillation pattern in thereactor spectrum for each of the two identified baselines(240 km and 350 km) and to distinguish them from otherantineutrino sources

The oscillation patterns from the more distant reactorsare less evident after they are combined There is still avisible feature at antineutrino energies of 45MeV from


an accumulation of reactors at distances of the order of550 km A detailed description of the spectrum at this energyis still under discussion [57] A preliminary study showsthat the combined systematic uncertainties associated withthe unoscillated spectrum description are below 5 Theseuncertainties can be reduced using for the distant reactors(source 3) direct measurements at close-by detectors likethose of Daya Bay [57]

74 Geoneutrinos and Earth Studies Interest in geoneutrinoshas increased in the last few years with significant collabo-rations between neutrino physicists and geo-physicists Jointresults may finally explain the radiogenic heat flow of theEarth

In SNO+ the geoneutrinos from the uranium and tho-rium chains can be detected These antineutrinos comemainly from thick continental crust with increases due tovariations in local crust components [58]

The energy spectra of geoneutrinos are well-known foreach of the standard decay chains [59] The effect of neutrinooscillations is largely averaged out due to the long range inproduction distances leading to a total survival probabilityof

⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579

12= 336∘ [42] Detailed studies of

the impact of the MSW effects on the energy spectrum are inprogress

As a first analysis step we will fix the total UTh ratioaccording to standard geological models [60] and fit for thetotal flux assuming a precise shape for the energy spectrumof geoneutrinos The possible effect of local variations ofthis ratio is being quantified together with that from thelow energy reactor spectrum Systematic uncertainties in theenergy scale and energy resolution and from the constraintson the alpha-n backgrounds will vary for each of the datataking phases Overall the SNO+ sensitivity to the totalflux is expected to be dominated by statistical uncertaintiesThe accuracy will be close to that of Borexino for similardata-taking periods the larger volume of the SNO+ detectorcompensates for the higher rate reactor background Weexpect a similar rate of geoneutrinos and reactor antineu-trinos in the 18MeVndash35MeV energy region However thereactor spectrum extends up to much higher energies andcontains features that can help in establishing the oscillationparameters The time evolution analysis will also help toseparate the reactor background (Section 73) In the Te-loaded phase the low energy backgrounds are expected tobe about 50ndash150 times higher than in the pure scintillatorphase which can make the extraction of the geoneutrinosignal more difficult

We aim to additionally separate both the uranium andthorium contributions and the mantle and crust contri-butions in a global analysis of the geoneutrino spectrumincluding data from KamLAND [61] and Borexino [62]

8 Supernova Neutrino Observation

The era of neutrino astronomy commenced with the obser-vation of 24 events all associated with the inverse beta decayof ]119890 from the collapse of supernova SN 1987A at sim50 kpc

[63] SNO+ with its large high purity liquid scintillatorvolume and the deep location underground is one of themostpromising experiments for the detection of neutrinos fromcore collapse supernovae (CCSNe) offering a rich sample ofdetection channels low backgrounds and a large number oftarget particles and nuclei CCSNe are an exceptional sourceof neutrinos of all flavors and types and a measurementis expected to shed light on the explosion mechanismThe shape of the individual supernova (SN) ]

120572(]120572

=]119890 ]119890 ]119909 where in this context ]

119909is the sum of ]

120583 ]120583 ]120591

and ]120591) energy spectra is expected to approximate a thermal

spectrum [64] in the absence of neutrino flavor changingmechanisms At postbounce times 119905 lt 1 s before shockrevival the flavor changes are expected to be reduced tothose induced by thewell-knownMSWeffect in a quasi-staticenvironment [65 66] At later times many further effectsinterfere significantly modifying the spectral shape Theseeffects are nontrivial and still lack a full understanding and aconsistent analytical treatment At present sensitivity studiesto thermal spectral parameters are only meaningful for atmost the first second of the burst It is estimated that half ofall neutrinos are emitted in this time span [67]

81 Signal Detection in SNO+ For the detection potential ofSNO+ presented in this paper we assume that the distancefrom the SN to Earth is 119889 = 10 kpc known from for examplethe detection of the electromagnetic radiation released inthe SN event and that 3 times 1053 erg of binding energy (120576])are released in the form of neutrinos equally partitionedamongst all six flavors and typesThe mean energies used are12MeV for ]

119890 15MeV for ]

119890 and 18MeV for ]

119909[68] which

are generic mean SN neutrino energies [69] consistent withthe findings from SN 1987A

The possible SN neutrino interaction channels during theSNO+ pure scintillator phase are listed in Table 5 togetherwith the expected event rates Several events due to ]

119890are

expected because of the comparatively large cross sectionfor the IBD reaction [70] This process seen during SN1987A is the only interaction of SN neutrinos observed todate Additionally SNO+ can measure the flux of ]

119909and ]

119890

As the mean neutrino energy is below about 30MeV ]119890s

and ]119890s will be detected mainly by the charged current (CC)

interactions while supernova ]119909s can only be detected by

the more challenging neutral current (NC) reactions OneNC reaction is neutrino-proton elastic scattering (ES) ] +p rarr ] + p [71] which is the only channel that providesspectral information about ]

119909s The total cross section of

this process [72] is about a factor of three smaller than thecross section of IBD however the reaction is possible for allsix neutrino types yielding a similar number of events for adetector threshold above sim02MeV

82 SNO+ Sensitivity to the ]119909Spectral Shape In the pre-

liminary estimations of the SNO+ sensitivity to ]119909

spectral


Table 5 Supernova neutrino interaction channels in LAB-PPOThe event rates per 780 tonnes of material assume the incomingneutrino time-integrated flux described in the text No flavorchanging mechanisms are considered The uncertainties on theevent rates only include the cross section uncertainties [16]

Reaction Number of eventsNC ] + p rarr ] + p 4291 plusmn 120a

CC ]119890

+ p rarr n + e+ 1947 plusmn 10

CC ]119890

+ 12C rarr 12Bgs + e+ 70 plusmn 07

CC ]119890

+ 12C rarr 12Ngs + eminus 27 plusmn 03

NC ] + 12C rarr 12Clowast(151MeV) + ]1015840 438 plusmn 87

CCNC ] + 12C rarr 11C or 11B + 119883 24 plusmn 05

]ndashelectron elastic scattering 131ba1189 plusmn 34 above a trigger threshold of 02MeV visible energy

bThe Standard Model cross section uncertainty is lt1

shape through ]-p ES we conservatively assume a spatialradius cut of 5m and a 02MeV threshold correspondingto a minimal neutrino energy of 119864min

] asymp 219MeV This isclose to the threshold we expect to use for events that willbe permanently stored We are currently discussing othersettings for the trigger thresholds to avoid any loss of potentiallow energy supernova events

In Figure 9 the reconstructed energy spectrum of allneutrinos emitted in the first second of the SN (]

119890 ]119890 and ]

119909)

and detected in SNO+ via the ]-p ES reaction is showntogether with the true neutrino spectrumThe reconstructedenergy spectrum is obtained from the detected proton energyunfolded using the TUnfold algorithm [73] on the basisof binned data The strongly nonlinear quenching of theproton energy which shifts most of the scattering eventsbelow sim05MeV electron equivalent energy and the finitedetector resolution are taken into account The number ofevents in the lowest bin is slightly overestimated due to bin-to-bin migrations caused by the finite energy resolution Thestatistical and total systematic uncertainties are also shown Afit to the ]

119909spectrum is only possible if the ]

119890and ]

119890spectra

aremeasured independently SNO+ is sensitive to the spectralshape of ]

119890s via the IBD reaction while in the case of ]

119890s it

has to be assumed that an independent detector with forexample a Pb target like HALO [74] or a LAr target [70]provides the necessary spectral information

The resulting best fit 119864] spectrum is also shown inFigure 9 and is in excellent agreement The systematicuncertainties propagated within the fit are the ]-p ES crosssection the number of target protons 119873p the ionizationquenching parameter the spectral ]

119890and ]

119890parameters

and the energy resolution of the detector The correspondingbest fit values are ⟨119864]

119909

⟩ = 178+35minus30

(stat)+02minus08

(syst) MeVand 120576]

119909

= (1025+823minus422

(stat)+162minus130

(syst)) times 1051 erg [16] whilethe respective expectation values are 18MeV and 100 times1051 erg

83 SNEWS SNO+ is preparing to participate in the inter-experiment Supernova EarlyWarning System (SNEWS) [75]which has the goal to provide a fast and reliable alert using the

True

Best fitReconstructed (black 120590stat blue 120590tot)

30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)

Figure 9 True reconstructed and best fit SN neutrino energydistribution of the ]-p ES detection channel within the FV andabove the detector threshold [16] Shown is the sum of the ]

119890

]119890

and ]

119909

spectra considering their time-integrated flux in the firstsecond of the reference SN The statistical uncertainties are shownin black while the total uncertainties are shown in blue Thecontribution from systematic uncertainty is too small to be resolved

coincident observation of burst signals in several operatingdetectors As neutrinos escape from the SN tens of minutesup to several hours before the first photons their detectionoffers the possibility of alerting the astronomical communityto the appearance of the next SN light signal

9 Exotic Physics Searches

Due to its location deep underground which significantlyreduces the cosmogenic background and the high radio-purity of the materials used SNO+ has a unique sensitivity tosearch for exotic physics including certain modes of nucleondecay and axion or axion-like particle searches

91 Invisible Nucleon Decay Nucleon decay modes to a finalstate undetected by the experiment for example n rarr 3]can be searched for by detecting the decay products of theremaining unstable nucleus as it deexcites This process hasbeen previously investigated by some experiments such asSNO [76] by searching for the decay of 16O nuclei andBorexino [77] and KamLAND [78] by looking for the decayof 12C nuclei We plan to search for the invisible nucleondecay of 16Oduring the initial water phase of the experimentIn the case of a decaying neutron the resulting 15O willdeexcite emitting a 618MeV gamma 44 of the time For adecaying proton the nucleus is left as 15N which in 41 ofthe decays deexcites emitting a 632MeV gamma [79] Boththese signals will be in a favorable region of the SNO+ energyspectrum (54MeVndash9MeV) in which few backgrounds areexpected These are (1) internal and external 208Tl and 214Bidecays (2) solar neutrinos and (3) reactor and atmospheric


Table 6 Expected backgrounds in the 54ndash9MeV energy regionduring six months of water fill A fiducial volume cut of 55m isapplied to all events The events after the cos 120579sun gt minus08 cut arealso shown 120598(n) and 120598(p) are the neutron and proton decay-modedetection efficiencies in the 55mFV and energy window

Decay source Events in six monthscos 120579sun gt minus08 Cut

214Bi 0 0208Tl 06 06Solar neutrinos 864 177Reactor antineutrinos 15 13External 214Bi-208Tl 92 89Total 977 285120598(n) 01089 01017120598(p) 01264 01129

antineutrinosThe expected contribution of each backgroundin the 54ndash9MeV energy region in six months of running isshown in Table 6 The targeted purity for the SNO+ internalwater is the average of the SNO collaborationrsquos H

2O and D

2O

levels (see Table 2) The purity can be measured in situ usingevents below 5MeV and cross checked using water assaysSolar neutrino events can be reduced by placing a cut onthe direction of the event which is reconstructed using thetopology of the detected Cherenkov light Reactor antineu-trino events can be tagged using a delayed coincidence Thebackground due to atmospheric neutrinos is expected to besmall based on SNO data [76]

The events in Table 6 are given for a fiducial volume cutof 55m which helps in reducing the external backgroundsAn additional cut at cos 120579sun gt minus08 relative to the solardirection further reduces the dominant solar backgroundremoving sim80 of the events with a sacrifice of sim10 onthe signals and the isotropic backgrounds Figure 10 showsthe energy spectrum of the water phase backgrounds solarneutrinos reactor antineutrinos and radioactive decays fromthe uranium and thorium chains after the two cuts areapplied It also shows the shapes based on the current bestlimits of the signal gammas from invisible proton [76] andneutron [78] decay

Using a Poisson method [80] we can set the lower limitat 90 CL on the invisible nucleon decay lifetime 120591 by

120591 gt119873nucleons times 120598 times 119891119879

11987890

(4)

where119873nucleons = 24 times 1032 120598 is the efficiency of detectingthe decay in the signal window from Table 6 119878

90 is theexpected signal events at 90 CL and 119891

119879is the live-time

of 05 years Assuming we reach the expected backgrounda limit of 120591n gt 125 times 1030 and 120591p gt 138 times 1030 yearsfor the decay of neutrons and protons respectively can beset This is an improvement over the existing limit set byKamLAND 120591 gt 58 times 1029 years by a factor of sim2 withjust six months of running time A likelihood approachis in development which is expected to provide a furtherimprovement on the limit

p decay (21 times 1029 yr)

n decay (58 times 1029 yr)

Internal 214Bi

Internal 208Tl

External 214Bi + 208Tl

1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar

Figure 10 Expected energy spectrum for the water phase back-grounds The signal from invisible proton [76] and neutron [78]decay is also shown A fiducial radius cut of 55m and a cuton cos 120579sun gt minus08 are applied

92 Axion-Like Particle Search An axion-like particle (ALP)is defined as a neutral pseudoscalar particle that exists as anextension to the QCD Lagrangian [81]

A possible reaction channel for ALP production in theSun is p + d rarr 3He + A where A is the ALP with anenergy of 55MeV [82] In SNO+ the couplings of ALPsto electrons 119892Ae photons 119892A120574 and nucleons 119892AN can beobserved mainly through Compton conversion (A + eminus rarreminus + 120574) and the axioelectric effect (A+ eminus +Z

119883rarr eminus +119885

119883

with119885119883the charge of the involved nucleus119883) In both cases

for lowALPmasses the signature ismonoenergetic atsim5MeVelectromagnetic energy deposition

Different strategies for different phases of SNO+ are usedfor the detection of ALPs In the water phase the mostlikely interaction is theCompton conversion which producesa Cherenkov ring with topology similar to that of 8B-neutrinos The main background events are very similar tothose described for the invisible nucleon decay search (seeSection 91) as the two signals have similar energies Howeversince the Compton conversion has a strong directional biaswe expect to remove a significant amount of isotropic back-grounds leaving 8B-neutrinos as the dominant one With 6months of water data due to the deeper location and largerfiducial volume we expect to approach the current limit setby Borexino [82]

The BGO collaboration proposed a separate limit on theALP couplings without having to assume axions interact viaCompton conversion [83] In this case the detection of solarALPs via the axioelectric effect which depends on the nucleuscharge as1198855

119883

could be particularly interesting during the Te-loaded phase Due to the significantly large tellurium massSNO+ has the possibility of improving the limit on the axion-electron coupling constant set by the BGO collaboration byseveral orders of magnitude


10 Conclusions

In this paper the broad physics program of the SNO+experiment is presented Three main data taking phases areplanned one with the detector filled with ultra-pure waterone with unloaded liquid scintillator and one with 234tonnes of tellurium loaded into the detector

The primary physics goal of SNO+ is a sensitive searchfor 0]120573120573-decay of 130Te We expect to set a lower limit onthe half-life of this process of 1198790]120573120573

12

gt 9times 1025 yr (90 CL) in5 years of data taking This limit corresponds to an effectiveMajorana mass ranging from 55 to 133meV at the top of theinverted neutrino mass hierarchy The possibility of loading10 times more tellurium in order to cover the majority of theinverted hierarchy region is under investigation

Along with the 0]120573120573-decay search SNO+ also has thepotential to measure the low energy solar neutrinos like pepneutrinos If the same purity levels as initially achieved byBorexino are reached SNO+ can measure the pep neutrinoswith an uncertainty less than 10 in one year of data takingwith pure liquid scintillator Additionally if the backgroundis low enough SNO+ can measure CNO neutrinos

Another physics topic that can be explored by SNO+ isthemeasurement of geoneutrinos in a geologically interestinglocation which will be complementary to the measurementsdone by Borexino and KamLAND Furthermore SNO+ canmeasure reactor antineutrinos which will help in reducingthe uncertainty on the oscillation parameters

With its depth and low background SNO+ has anextraordinary opportunity to measure the supernova ]

119909

energy spectrum for the first time This measurement pro-vides valuable information in order to probe and constrainsupernova dynamics Participation in SNEWS will furthersupport a reliable early warning to the astronomical commu-nity in the event of a nearby supernova

During the water fill SNO+ can search for exotic physicsand set competitive limits in the invisible nucleon decayof 16O

We expect to start operation with the water fill phasesoon followed by the liquid scintillator fill phase after a fewmonths of data taking The Te-loaded phase is foreseen in2017

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

Capital construction funds for the SNO+ experiment areprovided by the Canada Foundation for Innovation (CFI)This work has been in part supported by the Science andTechnology Facilities Council (STFC) of theUnitedKingdom(Grants nos STJ0010071 and STK0013291) the NaturalSciences and Engineering Research Council of Canada theCanadian Institute for Advanced Research (CIFAR) theNational Science Foundation national funds from Portugal

and European Union FEDER funds through the COMPETEprogram through FCT Fundacao para a Ciencia e a Tec-nologia (Grant no EXPLFIS-NUC15572013) the DeutscheForschungsgemeinschaft (Grant no ZU1235) the EuropeanUnionrsquos Seventh Framework Programme (FP72007-2013under the European Research Council (ERC) Grant Agree-ment no 278310 and the Marie Curie Grant Agreement noPIEF-GA-2009-253701) the Director Office of Science ofthe US Department of Energy (Contract no DE-AC02-05CH11231) the US Department of Energy Office of Sci-ence Office of Nuclear Physics (Award no DE-SC0010407)the US Department of Energy (Contract no DE-AC02-98CH10886) the National Science Foundation (Grant noNSF-PHY-1242509) and the University of California Berke-ley The authors acknowledge the generous support of theVale and SNOLAB staff

References

[1] K Zuber ldquoDouble-beta decayrdquo Contemporary Physics vol 45no 6 pp 491ndash502 2004

[2] AM SerenelliWCHaxton andC Pena-Garay ldquoSolarmodelswith accretion I Application to the solar abundance problemrdquoThe Astrophysical Journal vol 743 no 1 article 24 2011

[3] A Friedland C Lunardini andC Pena-Garay ldquoSolar neutrinosas probes of neutrino-matter interactionsrdquo Physics Letters B vol594 no 3-4 pp 347ndash354 2004

[4] W C Haxton and A M Serenelli ldquoCN-cycle solar neutrinosand the Sunrsquos primordial core metallicityrdquo The AstrophysicalJournal vol 687 no 1 pp 678ndash691 2008

[5] M C Chen ldquoThe SNO liquid scintillator projectrdquo NuclearPhysics BmdashProceedings Supplements vol 145 no 1ndash3 pp 65ndash682005

[6] B Aharmim S N Ahmed T C Andersen et al ldquoMeasurementof the cosmic ray and neutrino-induced muon flux at theSudbury Neutrino Observatoryrdquo Physical Review D vol 80 no1 Article ID 012001 2009

[7] J Boger R L Hahn J K Rowley et al ldquoThe Sudbury NeutrinoObservatoryrdquo Nuclear Instruments and Methods in PhysicsResearch A vol 449 no 1-2 pp 172ndash207 2000

[8] N Jelley A B McDonald and R G H Robertson ldquoTheSudbury Neutrino Observatoryrdquo Annual Review of Nuclear andParticle Science vol 59 pp 431ndash465 2009

[9] P G Jones Background rejection for the neutrinoless double-beta decay experiment SNO+ [PhD thesis] Lincoln CollegeOxford UK 2011 httpethosblukOrderDetailsdouin=ukblethos559770

[10] M Yeh S Hans W Beriguete et al ldquoA new water-based liquidscintillator and potential applicationsrdquoNuclear Instruments andMethods in Physics Research Section A Accelerators Spectrom-eters Detectors and Associated Equipment vol 660 no 1 pp51ndash56 2011

[11] H M OrsquoKeeffe E OrsquoSullivan and M C Chen ldquoScintillationdecay time and pulse shape discrimination in oxygenatedand deoxygenated solutions of linear alkylbenzene for theSNO+ experimentrdquoNuclear Instruments andMethods in PhysicsResearch A vol 640 no 1 pp 119ndash122 2011

[12] S Grullon ldquoLight yield and scintillation decay time constantsof Te-loaded liquid scintillator for the SNO+ experimentrdquo in


Proceedings of the 26th International Conference on NeutrinoPhysics and Astrophysics (Neutrino rsquo14) Boston UniversityBoston Mass USA June 2014

[13] HWanChanTseung J Kaspar andNTolich ldquoMeasurement ofthe dependence of the light yields of linear alkylbenzene-basedand EJ-301 scintillators on electron energyrdquoNuclear Instrumentsand Methods in Physics Research Section A Accelerators Spec-trometers Detectors and Associated Equipment vol 654 no 1pp 318ndash323 2011

[14] H Wan Chan Tseung and N Tolich ldquoEllipsometric measure-ments of the refractive indices of linear alkylbenzene and EJ-301scintillators from 210 to 1000 nmrdquo Physica Scripta vol 84 no3 Article ID 035701 2011

[15] B von Krosigk L Neumann R Nolte S Rottger and K ZuberldquoMeasurement of the proton light response of various LABbased scintillators and its implication for supernova neutrinodetection via neutrino-proton scatteringrdquoThe European Physi-cal Journal C vol 73 article 2390 2013

[16] B vonKrosigkMeasurement of proton and 120572-particle quenchingin LAB based scintillators and determination of spectral sensitiv-ities to supernova neutrinos in the SNO+ detector [PhD thesis]Technische Universitat Dresden Dresden Germany 2015

[17] J B Birks The Theory and Practice of Scintillation CountingPergamon Press New York NY USA 1964

[18] R Ford M Chen O Chkvorets D Hallman and E Vazquez-Jauregui ldquoSNO+ scintillator purification and assayrdquo AIP Con-ference Proceedings vol 1338 pp 183ndash194 2011

[19] R J Ford ldquoA scintillator purification plant and fluid handlingsystem for SNO+rdquoAIPConference Proceedings vol 1672 ArticleID 080003 2015

[20] C Arpesella H O Back M Balata et al ldquoDirect measurementof the 7Be solar neutrino flux with 192 days of borexino datardquoPhysical Review Letters vol 101 no 9 Article ID 091302 2008

[21] K Eguchi S Enomoto K Furuno et al ldquoFirst results fromKamLAND evidence for reactor antineutrino disappearancerdquoPhysical Review Letters vol 90 no 2 Article ID 021802 2003

[22] S Hans R Rosero L Hu et al ldquoPurification of telluric acid forSNO+ neutrinoless double-beta decay searchrdquo Nuclear Instru-ments and Methods in Physics Research Section A AcceleratorsSpectrometers Detectors and Associated Equipment vol 795 pp132ndash139 2015

[23] R Alves S Andringa S Bradbury et al ldquoThe calibration systemfor the photomultiplier array of the SNO+ experimentrdquo Journalof Instrumentation vol 10 no 3 Article ID P03002 2015

[24] NationalNuclearDataCenter ldquoNuclear structureamp decay datardquohttpwwwnndcbnlgovnudat2

[25] G Alimonti C Arpesella M B Avanzini et al ldquoThe liquidhandling systems for the Borexino solar neutrino detectorrdquoNuclear Instruments and Methods in Physics Research SectionA Accelerators Spectrometers Detectors and Associated Equip-ment vol 609 no 1 pp 58ndash78 2009

[26] F Alessandria E Andreotti R Ardito et al ldquoCUORE crys-tal validation runs results on radioactive contamination andextrapolation to CUORE backgroundrdquo Astroparticle Physicsvol 35 no 12 pp 839ndash849 2012

[27] T W Armstrong K C Chandler and J Barish ldquoCalculationsof neutron flux spectra induced in the Earthrsquos atmosphere bygalactic cosmic raysrdquo Journal of Geophysical Research vol 78no 16 pp 2715ndash2726 1973

[28] N Gehrels ldquoInstrumental background in balloon-bornegamma-ray spectrometers and techniques for its reductionrdquoNuclear Instruments and Methods in Physics Research SectionA Accelerators Spectrometers Detectors and AssociatedEquipment vol 239 no 2 pp 324ndash349 1985

[29] G Alimonti G Angloher C Arpesella et al ldquoMeasurementof the 14C abundance in a low-background liquid scintillatorrdquoPhysics Letters B vol 422 no 1ndash4 pp 349ndash358 1998

[30] S Abe S Enomoto K Furuno et al ldquoProduction of radioac-tive isotopes through cosmic muon spallation in KamLANDrdquoPhysical Review C vol 81 no 2 Article ID 025807 2010

[31] G Bellini J Benziger D Bick et al ldquoPrecision measurementof the 7Be solar neutrino interaction rate in Borexinordquo PhysicalReview Letters vol 107 no 14 Article ID 141302 2011

[32] C Galbiati A Pocar D Franco A Ianni L Cadonati andS Schonert ldquoCosmogenic 11C production and sensitivity oforganic scintillator detectors to pep and CNO neutrinosrdquoPhysical Review C vol 71 no 5 Article ID 055805 2005

[33] G Bellini J Benziger D Bick et al ldquoFirst evidence of pepsolar neutrinos by direct detection in BorexinordquoPhysical ReviewLetters vol 108 no 5 Article ID 051302 6 pages 2012

[34] V Lozza and J Petzoldt ldquoCosmogenic activation of a naturaltellurium targetrdquo Astroparticle Physics vol 61 pp 62ndash71 2015

[35] E Arushanova ldquoPileup background rejection in SNO+ exper-imentrdquo in Proceedings of the Joint Particle Astroparticle andNuclear Physics Groups Annual Meeting (IoP rsquo15) ManchesterUK April 2015

[36] E Arushanova and A R Back ldquoProbing neutrinoless doublebeta decay withSNO+rdquo httparxivorgabs150500247

[37] I Lawson and B Cleveland ldquoLow background counting atSNOLABrdquo in Proceedings of the Topical Workshop on LowRadioactivity Techniques (LRT rsquo10) vol 1338 of AIP ConferenceProceedings pp 68ndash77 Sudbury Canada August 2010

[38] B Aharmim S N Ahmed A E Anthony et al ldquoElectronenergy spectra fluxes and day-night asymmetries of 8B solarneutrinos from measurements with NaCl dissolved in theheavy-water detector at the Sudbury Neutrino ObservatoryrdquoPhysical Review C vol 72 no 5 Article ID 055502 47 pages2005

[39] N J T Smith ldquoFacility and science developments at SNOLABrdquoin Proceedings of the ASPERA Workshop The Next GenerationProjects in Deep Underground Laboratories Zaragoza SpainJune 2011 httpindicocernchevent130734contribution21materialslides0pdf

[40] M Redshaw B J Mount E G Myers and F T Avignone IIIldquoMasses of 130Te and 130Xe anddouble-120573-decayQvalue of 130TerdquoPhysical Review Letters vol 102 no 21 Article ID 212502 4pages 2009

[41] R Arnold C Augier J Baker et al ldquoMeasurement of the 120573120573decay half-life of 130Te with the NEMO-3 Detectorrdquo PhysicalReview Letters vol 107 no 6 Article ID 062504 2011

[42] B Aharmim S N Ahmed A E Anthony et al ldquoCombinedanalysis of all three phases of solar neutrino data from theSudbury Neutrino Observatoryrdquo Physical Review C vol 88 no2 Article ID 025501 2013

[43] J Barea J Kotila and F Iachello ldquoNuclear matrix elements fordouble-120573 decayrdquo Physical Review C vol 87 no 1 Article ID014315 2013

[44] J Kotila and F Iachello ldquoPhase-space factors for double-120573decayrdquoPhysical ReviewCmdashNuclear Physics vol 85 no 3 ArticleID 034316 2012


[45] F Simkovic V Rodin A Faessler and P Vogel ldquo0]120573120573 and2]120573120573 nuclear matrix elements quasiparticle random-phaseapproximation and isospin symmetry restorationrdquo PhysicalReview C vol 87 no 4 Article ID 045501 2013

[46] J Menendez A Poves E Caurier and F Nowacki ldquoDisassem-bling the nuclear matrix elements of the neutrinoless 120573120573 decayrdquoNuclear Physics A vol 818 no 3-4 pp 139ndash151 2009

[47] J Hyvarinen and J Suhonen ldquoNuclear matrix elements for0]120573120573 decays with light or heavy Majorana-neutrino exchangerdquoPhysical Review C vol 91 no 2 Article ID 024613 2015

[48] T R Rodrıguez and G Martınez-Pinedo ldquoEnergy densityfunctional study of nuclear matrix elements for neutrinoless120573120573 decayrdquo Physical Review Letters vol 105 no 25 Article ID252503 2010

[49] M Asplund N Grevesse A J Sauval and P Scott ldquoThe chem-ical composition of the sunrdquo Annual Review of Astronomy andAstrophysics vol 47 pp 481ndash522 2009

[50] S Abe K Furuno A Gando et al ldquoMeasurement of the 8B solarneutrino flux with the KamLAND liquid scintillator detectorrdquoPhysical ReviewC vol 84 no 3 Article ID035804 6 pages 2011

[51] G Bellini J Benziger S Bonetti et al ldquoMeasurement of thesolar 8B neutrino rate with a liquid scintillator target and 3MeVenergy threshold in the Borexino detectorrdquo Physical Review Dvol 82 no 3 Article ID 033006 2010

[52] M Smy ldquoResults from Super-Kamiokanderdquo in Proceedingsof the 25th International Conference on Neutrino Physics andAstrophysics (Neutrino rsquo12) Kyoto Japan June 2012

[53] A Renshaw ldquoSolar neutrino results from Super-KamiokanderdquoPhysics Procedia vol 61 pp 345ndash354 2015

[54] R Bonventre A LaTorre J R Klein G D Orebi Gann S Seib-ert andOWasalski ldquoNonstandardmodels solar neutrinos andlarge 120579

13

rdquo Physical Review D vol 88 no 5 Article ID 0530102013

[55] G Bellini J Benziger D Bick et al ldquoNeutrinos from theprimary proton-proton fusion process in the Sunrdquo Nature vol512 no 7515 pp 383ndash386 2014

[56] AGando Y Gando K Ichimura et al ldquoConstraints on 12057913

froma three-flavor oscillation analysis of reactor antineutrinos atKamLANDrdquoPhysical ReviewD vol 83 no 5 Article ID 0520022011

[57] F P An A B Balantekin H R Band et al ldquoSpectral mea-surement of electron antineutrino oscillation amplitude andfrequency at Daya Bayrdquo Physical Review Letters vol 112 no 6Article ID 061801 2014

[58] H K C Perry J-C Mareschal and C Jaupart ldquoEnhancedcrustal geo-neutrino production near the Sudbury NeutrinoObservatory Ontario Canadardquo Earth and Planetary ScienceLetters vol 288 no 1-2 pp 301ndash308 2009

[59] S Enomoto ldquoUsing Neutrinos to study the earth geo-neutrinosrdquo in Proceedings of the 13th International Workshop onNeutrino Telescopes (NeuTel rsquo09) Venice Italy March 2009

[60] A M Dziewonski and D L Anderson ldquoPreliminary referenceEarth modelrdquo Physics of the Earth and Planetary Interiors vol25 no 4 pp 297ndash356 1981

[61] A Gando Y Gando K Ichimura et al ldquoPartial radiogenicheat model for Earth revealed by geoneutrino measurementsrdquoNature Geoscience vol 4 pp 647ndash651 2011

[62] G Bellini J Benziger D Bick et al ldquoMeasurement of geo-neutrinos from 1353 days of Borexinordquo Physics Letters B vol722 no 4-5 pp 295ndash300 2013

[63] I V Krivosheina ldquoSN 1987Amdashhistorical view about registrationof the neutrino signal with BAKSAN Kamiokande II and IMBdetectorsrdquo International Journal ofModern Physics D vol 13 no10 Article ID 2085 2004

[64] M T Keil G G Raffelt and H-T Janka ldquoMonte Carlo studyof supernova neutrino spectra formationrdquo The AstrophysicalJournal vol 590 no 2 pp 971ndash991 2003

[65] J Xu M-Y Huang L-J Hu X-H Guo and B-L YoungldquoDetection of supernova neutrinos on the earth for large 120579

13

rdquoCommunications in Theoretical Physics vol 61 no 2 pp 226ndash234 2014

[66] S Sarikas G G Raffelt L Hudepohl and H-T Janka ldquoSup-pression of self-induced flavor conversion in the Supernovaaccretion phaserdquo Physical Review Letters vol 108 no 6 ArticleID 061101 2012

[67] G Pagliaroli F Vissani M L Costantini and A IannildquoImproved analysis of SN1987A antineutrino eventsrdquo Astropar-ticle Physics vol 31 no 3 pp 163ndash176 2009

[68] B Dasgupta and J F Beacom ldquoReconstruction of supernova]120583

]120591

anti-]120583

and anti-]120591

neutrino spectra at scintillatordetectorsrdquo Physical Review D vol 86 no 11 Article ID 1130062011

[69] T Lund and J P Kneller ldquoCombining collective MSW andturbulence effects in supernova neutrino flavor evolutionrdquoPhysical Review D vol 88 no 2 Article ID 023008 2013

[70] K Scholberg ldquoSupernova neutrino detectionrdquo Annual Reviewof Nuclear and Particle Science vol 62 pp 81ndash103 2012

[71] J F Beacom W M Farr and P Vogel ldquoDetection of super-nova neutrinos by neutrino-proton elastic scatteringrdquo PhysicalReview D vol 66 no 3 Article ID 033001 2002

[72] L A Ahrens S H Aronson P L Connolly et al ldquoMeasurementof neutrino-proton and antineutrino-proton elastic scatteringrdquoPhysical Review D vol 35 no 3 pp 785ndash809 1987

[73] S Schmitt ldquoTUnfold an algorithm for correcting migrationeffects in high energy physicsrdquo Journal of Instrumentation vol7 no 10 Article ID T10003 2012

[74] D Vaananen and C Volpe ldquoThe neutrino signal at HALOlearning about the primary supernova neutrino fluxes andneutrino propertiesrdquo Journal of Cosmology and AstroparticlePhysics vol 2011 article 019 2011

[75] P Antonioli R T Fienberg F Fleurot et al ldquoSNEWS theSuperNova Early Warning Systemrdquo New Journal of Physics vol6 article 114 2004

[76] S N Ahmed A E Anthony E W Beier et al ldquoConstraints onnucleon decay via invisible modes from the Sudbury NeutrinoObservatoryrdquo Physical Review Letters vol 92 no 10 Article ID102004 4 pages 2004

[77] H O Back M Balata A de Bari et al ldquoNew limits on nucleondecays into invisible channels with the BOREXINO countingtest facilityrdquo Physics Letters B vol 563 no 1-2 pp 23ndash34 2003

[78] T Araki S Enomoto K Furuno et al ldquoSearch for the invisibledecay of neutronswithKamLANDrdquoPhysical ReviewLetters vol96 no 10 Article ID 101802 5 pages 2006

[79] H Ejiri ldquoNuclear deexcitations of nucleon holes associated withnucleon decays in nucleirdquo Physical Review C vol 48 no 3 pp1442ndash1444 1993

[80] O Helene ldquoUpper limit of peak areardquo Nuclear Instruments andMethods In Physics Research vol 212 no 1ndash3 pp 319ndash322 1983


[81] P W Graham I G Irastorza S K Lamoreaux A Lindner andK A van Bibber ldquoExperimental searches for the axion andaxion-like particlesrdquo Annual Review of Nuclear and ParticleScience vol 65 no 1 pp 485ndash514 2015

[82] G Bellini J Benziger D Bick et al ldquoSearch for solar axionsproduced in the p(d 3He)A reaction with Borexino detectorrdquoPhysical Review D vol 85 no 9 Article ID 092003 2012

[83] A V Derbin L Gironi S S Nagorny et al ldquoSearch for axioelec-tric effect of solar axions using BGO scintillating bolometerrdquoTheEuropean Physical Journal C vol 74 no 9 article 3035 2014

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


FluidsJournal of

Atomic and Molecular Physics

Journal of



Advances in Condensed Matter Physics

OpticsInternational Journal of



AstronomyAdvances in

International Journal of


Superconductivity


Statistical MechanicsInternational Journal of


GravityJournal of


AstrophysicsJournal of


Physics Research International


Solid State PhysicsJournal of

Computational Methods in Physics

Journal of



Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014


PhotonicsJournal of


Journal of

Biophysics


ThermodynamicsJournal of


15TRIUMF 4004 Wesbrook Mall Vancouver BC Canada V6T 2A316Brookhaven National Laboratory Chemistry Department Building 555 PO Box 5000 Upton NY 11973-500 USA17Center for Experimental Nuclear Physics and Astrophysics and Department of Physics University of Washington SeattleWA 98195 USA

18Norwich University 158 Harmon Drive Northfield VT 05663 USA19Physics Department Lancaster University Lancaster LA1 4YB UK20Institut fur Kern- und Teilchenphysik Technische Universitat Dresden Zellescher Weg 19 01069 Dresden Germany21Departamento de Fısica Faculdade de Ciencias Universidade de Lisboa Campo Grande Edifıcio C8 1749-016 Lisboa Portugal22Department of Physics University of Liverpool Liverpool L69 3BX UK23Department of Physics and Astronomy University of Sheffield Hicks Building Hounsfield Road Sheffield S3 7RH UK24Department of Chemistry amp Physics Armstrong Atlantic State University 11935 Abercorn Street Savannah GA 31419 USA25Instituto de Fısica Universidad Nacional Autonoma de Mexico (UNAM) Apartado Postal 20-364 01000 Mexico DF Mexico

Correspondence should be addressed to V Lozza valentinalozzatu-dresdende

Received 22 July 2015 Accepted 22 November 2015

Academic Editor Vincenzo Flaminio

Copyright copy 2016 S Andringa et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited Thepublication of this article was funded by SCOAP3

SNO+ is a large liquid scintillator-based experiment located 2 kmunderground at SNOLAB Sudbury Canada It reuses the SudburyNeutrino Observatory detector consisting of a 12m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pureliquid scintillator Designed as a multipurpose neutrino experiment the primary goal of SNO+ is a search for the neutrinolessdouble-beta decay (0]120573120573) of 130Te In Phase I the detectorwill be loadedwith 03natural tellurium corresponding to nearly 800 kgof 130Te with an expected effective Majorana neutrino mass sensitivity in the region of 55ndash133meV just above the inverted masshierarchy Recently the possibility of deploying up to ten times more natural tellurium has been investigated which would enableSNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future AdditionallySNO+ aims tomeasure reactor antineutrino oscillations low energy solar neutrinos and geoneutrinos to be sensitive to supernovaneutrinos and to search for exotic physics A first phase with the detector filled with water will begin soon with the scintillatorphase expected to start after a few months of water data taking The 0]120573120573 Phase I is foreseen for 2017

1 Introduction

SNO+ is a large-scale liquid scintillator experiment located ata depth of 5890 plusmn 94meter water equivalent (mwe) in ValersquosCreighton mine in Sudbury Canada The deep undergroundlocation the high purity of materials used and the largevolumemake SNO+an ideally suited detector to study severalaspects of neutrino physics

The main goal of SNO+ is a search for the neutrinolessdouble-beta decay (0]120573120573) of 130Te 0]120573120573-decay is a rarenuclear process that will happen if neutrinos are Majorana-type particles that is they are their own antiparticlesUnderstanding the Majorana nature of neutrinos is one ofthe most active areas of research inmodern neutrino physicsTheobservation of the 0]120573120573-decaywould demonstrate leptonnumber violation a key ingredient in the theory of leptogen-esis The process can be seen as two simultaneous 120573-decaysin which two neutrons are converted into two protons andtwo electrons as the neutrinos from the two weak verticesmutually annihilate The signature is a peak at the 119876-valueof the process in the summed energy spectrum of the twoelectrons The measured quantity is the half-life of the decayThe effective Majorana neutrino mass 119898

120573120573 which is highly

dependent on the nuclear matrix elements is derived fromthe half-life as described in [1] A half-life of the order of 1025

years corresponds to a neutrino mass range of about 200ndash400meVThe large mass and low background of SNO+ allowthe investigation of such a rare event

The large volume and the high radio-purity are also thereason why SNO+ can explore several other physics topicsObservation of geoneutrinos will help in understandingthe mechanisms for heat production in the Earth Reactorantineutrino measurements constrain the neutrino oscilla-tion parameters Neutrinos and antineutrinos coming fromsupernova explosions would help to answermany unresolvedquestions in neutrino astronomy Additionally SNO+ has thepotential to search for exotic physics like axion-like particlesand invisible nucleon decay

The depth of SNOLAB also provides the opportunityto measure low energy solar neutrinos like pep and CNOneutrinos The pep neutrinos are monoenergetic with anenergy of 144MeV and a very well predicted flux with anuncertainty of 12 constrained by the solar luminosity [2]A precise measurement of the flux can probe the MikheyevSmirnov and Wolfenstein (MSW) effect of neutrino mixingas well as alternatemodels likeNon Standard Interactions [3]Another open question in the solar neutrino field is related tothe solar metallicity The Standard Solar Model was alwaysin excellent agreement with helioseismology until recentanalyses suggested a metallicity about 30 lower than the

















































12










4 Backgrounds







12= 1643 120583s





214Bi

210Bi

210Tl

206Pb

210Pb

210Po

214Po

Q-value = 562MeV

T12 = 13min

T12 = 199min

T12 = 501d

T12 = 222 yr

T12 = 1643120583s

T12 = 1384d


gt99 120573-decay

Q-value = 548MeV



Q-value = 783MeV

Q-value = 327MeV


0021 120572-decay





=




2



a



b






12= 222 yr119876-value = 006MeV)


12= 50 d 119876-value = 116MeV)

and 210Po (11987912

= 1384 d 119864120572










12=


212Bi

208Tl

208Pb

212Po


T12 = 31min

T12 = 606min

T12 = 0299120583s













12= 269 yr) and 85Kr (119879




12=










12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912


























a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



















































12










4 Backgrounds







12= 1643 120583s





214Bi

210Bi

210Tl

206Pb

210Pb

210Po

214Po

Q-value = 562MeV

T12 = 13min

T12 = 199min

T12 = 501d

T12 = 222 yr

T12 = 1643120583s

T12 = 1384d


gt99 120573-decay

Q-value = 548MeV



Q-value = 783MeV

Q-value = 327MeV


0021 120572-decay





=




2



a



b






12= 222 yr119876-value = 006MeV)


12= 50 d 119876-value = 116MeV)

and 210Po (11987912

= 1384 d 119864120572










12=


212Bi

208Tl

208Pb

212Po


T12 = 31min

T12 = 606min

T12 = 0299120583s













12= 269 yr) and 85Kr (119879




12=










12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912


























a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




214Bi

210Bi

210Tl

206Pb

210Pb

210Po

214Po

Q-value = 562MeV

T12 = 13min

T12 = 199min

T12 = 501d

T12 = 222 yr

T12 = 1643120583s

T12 = 1384d


gt99 120573-decay

Q-value = 548MeV



Q-value = 783MeV

Q-value = 327MeV


0021 120572-decay





=




2



a



b






12= 222 yr119876-value = 006MeV)


12= 50 d 119876-value = 116MeV)

and 210Po (11987912

= 1384 d 119864120572










12=


212Bi

208Tl

208Pb

212Po


T12 = 31min

T12 = 606min

T12 = 0299120583s













12= 269 yr) and 85Kr (119879




12=










12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912


























a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics











12=


212Bi

208Tl

208Pb

212Po


T12 = 31min

T12 = 606min

T12 = 0299120583s













12= 269 yr) and 85Kr (119879




12=










12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912


























a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics









12= 602 d 119876-value =

290MeV) 22Na (11987912

= 9506 d 119876-value = 284MeV) 60Co(11987912

= 1925 d119876-value = 282MeV) 110mAg (11987912


























a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics














a [7] 128 times 107









Futurephase

1st phase(now)

03 05 1 3 5




















0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics













0120573120573 (200meV)2120573120573



23 24 25 26 27 28 29 322

T120573120573 (MeV)

0

10

20

30

40

50

24 26 2822

T120573120573 (MeV)

020406080

100120

Cou

nts5

yr20

keV

bin

Cts5

yr122

keV


120573120573


120573120573



119878 = 120598 sdot 119873130


1198790]12057312057312

(1)



12


12

gt

9 times 1025 yr at 90 CL (1198790]12057312057312






12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics





12
















(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




(11987912






Energy (MeV)03 04 05 06 1 2 3 4 5 6

1

10

102

103

104

105

106

Sum8B7BeCNOpep


Even

ts002

MeV

yea












119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








119864]119890


≃ 119864prompt + 08MeV(2)


119890events depend




1 2 3 4 5 6 7 8 90 10Nu E (MeV)

0

10

20

30

40

50

60

70

80

90

(TN

UM

eV)



12


12










⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








⟨119875119890119890⟩ = cos4120579

13sdot (1 minus

sin2 (212057912)

2) + sin4120579

13≃ 0547 (3)

where 12057913= 91∘ and 120579








120572(]120572



120583 ]120583 ]120591




119890 15MeV for ]


119909[68] which



119890are


119909and ]

119890









spectral




CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics






CC ]119890


CC ]119890


CC ]119890









119890 ]119890 and ]

119909)



119890and ]

119890spectra



119890s it



119890and ]

119890parameters


119909

⟩ = 178+35minus30

(stat)+02minus08


119909

= (1025+823minus422

(stat)+162minus130



True


30 35 40 45 50 55 60 65 702505

101520253035404550

Cou

nts

(bin1

s045

kt)

E (MeV)


119890

]119890

and ]

119909











2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








2O and D

2O





11987890

(4)







Internal 214Bi

Internal 208Tl


1 2 3 4 5 6 7 8 9 100Energy (MeV)

10minus1

1

10

102

103

104

Even

ts pe

r yea

r per

02

MeV

Reactor Solar





119883





119883



10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




10 Conclusions



12





119909






Acknowledgments



References


























































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics
















































13














13





]120591

anti-]120583

and anti-]120591























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics












FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



Review Article Current Status and Future Prospects of the...

Documents

Transcript of Review Article Current Status and Future Prospects of the...