Super-Kamiokande R&D project SK-IV

Prospect for detection of supernova neutrinoNOW2014Sep. 9th, 2014Otranto, Lecce, Italy

Takaaki Morifor the Super-Kamiokande CollaborationOkayama University, Japan0ContentsSupernova burst neutrinosSupernova relic neutrinosGADZOOKS!Pre-supernova neutrinos1Neutrino from supernovaA supernova explosion happens when a star at least 8 times more massive than the sun collapses.

Released gravitational energy: ~3x1053 erg. Neutrinos carry almost all (99%) of the energy.

Supernova neutrinos detection provides a lot of informationCollapse physicsNeutrino Physics

Detection of SN neutrino is very important2

Livermore simulation:APJ, 496, 216 (1998)LuminosityAverage E2

Supernova burst detectors in the world(running and near future underground experiments)

Super-KKamLANDBaksan

LVD

Borexino

SNO+(under construction)

IceCube

HALO

Detectors on surface likeNOvA (14kton liquid scintillator(LS)),Daya Bay (160ton Gd-doped LS)can also be supernova detectors. 3

Super-Kamiokande32 kton water Cherenkov detectorDominant interaction is IBD (ne+p)( ~7300 events in total ~8000 events for 10kpc SN)Enough statistics to discuss model predictionsGood directionality for ne scattering (~300 events)

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SN monitor is running 24 hours a dayAnnounce the SN neutrino detection and its direction to the world within an hour4IceCube5

High statistics0.75% stat. error @ 0.5 sec and 100 ms bins[sec]From L.Koepke~kilometer long strings of PMTs in clear ice

Although multi-GeV energy threshold, may see burst as coincident increase in single PMT count rate

Cannot tag flavor, or other event-by-event info, but map overall burst time structure Liquid scintillator detectorsExpected number of events for 10 kpc SN

Inverse beta : ~300 events/ktonSpectrum measurement with good energy resolution

CC on 12C : ~ 30 events/kton

Electron scattering : ~20 events/kton

NC g from 12C : ~60 events/ktonTotal neutrino flux, 15.11 MeV mono energetic g

n + p NC : ~ 300 events/ktonSensitive to all types of neutrinos ( Independent from neutrino osc.)6From K.Inoue, G.Belliini, M.Chen

Spectrum @KamLAND

(Flux:PRD67,023004 (2003))

Supernova Relic Neutrino77Supernova Relic Neutrino8In the Universe, there exist SRN emitted from the past supernovae explosion

Expected SRN events : 1.3~6.7 events/year/22.5kton ( 10-30 MeV )Large target mass and high background reduction are necessaryTime

SRN predictions(ne fluxes)Neutrino flux (/cm2/sec/MeV)SRN mode : PRD, 79, 083013 (2009)Neutrino Energy[ MeV]8SRN search at Super-K9e+protongneneutronproton2.2 MeV g(Not efficiently detected)Search for SRN is limited by backgroundNeed to identify neutron to suppress the atmospheric neutrino background K.Bays et al.,PRD85(2012)

data CCe CCNC elastic/ > C. thr.all backgroundSRN255075Energy [MeV]Super-K has the best sensitivity to the SRN via IBD interactionfluxBy neutron tagging, direction accuracy can be improved to ~3 deg.Flux and spectrum : Livermore simulation1112

Item to study with EGADSEffect to Water transparencyWater purification systemNeutron detection efficiencyEtc.

EGADS experiment(Evaluating Gadoliniums Action on Detector System)1213

Selective filtration system(Water purification system)UDEAL(Water Transparency measurement device)200 m3 detector(240 photo sensor)15 m3 tank and pre-treatment system13

Current status of EGADS14achieve same level pure water transparencyachieve 86.2% of pure water cases14

Current status of EGADS15

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Current status of EGADS1616

Current status of EGADS17we found bad material, which is not used in SK detector17

Current status of EGADS1818Transparency of Gd-doped water19

w/o PMT60657075808590Cherenkov light left ( %)19

BGOAm/Be

Measurement of Gd g

DT[ms]Total electron Energy[MeV]Events / # of prompt trg.Events / # of prompt trg.241Am 237Np + a 9Be + a 12C + g(4.4MeV)+ nGd gGate500msecDelayed signalPrompt signalScintillationGd2(SO4)3 concentration: 200 ppm 20Pre-supernova neutrino detection21Pre-supernova neutrinos22

Importance of detectionInvestigation of mechanism of evolution of star at final at stage and collapseAlarm before the SN neutrino burst

TargetAntares (~170pc)Betelgeuse (~150pc)Gamma Velorum (~340pc)ACTA PHYSICAL POLONOCA B 40, 3063 (2009)Shell Si startsCore Si burningDirect pre-collapse stageShock breakoutSN neutrino burstLog Ln [erg/s]Neutrino is emitted in Si burning phase before core-collapse supernova22Pre-SN neutrino detection @ KamLAND23

Expected number of events @KamLAND

The early alarm will be issued from 3 days to 5 hours before from core-collapse

SignificanceNormal hierarchyInverted hierarchy

Flux@1pc(106/cm2/s/MeV)Anti ne energy [ MeV ]From K.IshidoshiroTime[day]23

Reactor + spallationBetelgeuse@GADZOOKS!Pre-SN neutrino detection by GADZOOKS!Like KamLAND, SK(GADZOOKS) will try for a very early alarm

In case of Betelgeuse assuming distance is 0.13 kpc# of only neutron signals in IBD interactionA.Odrzywolek et al., AIP Conf. Proc. 944, 109 (2007)2425SummarySupernova burst neutrinosSN neutrino provides a lot of information by energy, flavor, timing..Many detectors are waiting a SN burst

Supernova relic neutrinosR&D project for GADZOOKS! is ongoing

Supernova neutrino at Si burning stageIts detection provide the very early alarm for supernova burstKamLAND and GADZOOKS! can get precursor

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S.Ando, NNN05

Supernova Relic Neutrinos

S.Ando, Astrophys.J.607:20-31,2004.

~1017 supernovae so far.30

Super-KLVDIceCube

Borexino

snews.bnl.govSNEWS: SuperNova Early Warning SystemKamLAND

Daya Bay(soon)31

Supernova burst detectors in the world(running and near future underground experiments)

Super-KamiokandeKamLANDBaksan

LVD

Borexino

SNO+(under construction)

IceCube

HALO

Detectors on surface likeNOvA (14kton liquid scintillator(LS)),Daya Bay (160ton Gd-doped LS)can also be supernova detectors. 32Current Liquid scintillator detectors

KamLAND(1kton)Borexino(0.33kton)SNO+(1kton)under constructionLVD(1kton)NOnA(14kton)liquid and solid alert to astronomers experimentUT timesignificance10 secondcoincidenceby UT time stamp Coincidence Server at BNLSNEWS: SuperNova Early Warning System

- Neutrinos (and GW) precede em radiation by hours or even days- For promptness, require coincidence to suppress false alerts

- Running smoothly for more than 10 years, automated since 2005 - Amateur astronomer connectionsnews.bnl.gov

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UDEAL38

Pre-treat system39

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Gd removal system41

v42

Supernova burst detectors in the world(running and near future underground experiments)

Super-KKamLANDBaksan

LVD

Borexino

SNO+(under construction)

IceCube

HALO

76 ton Pb, 3He counter~ 40 ev.1 kton liq.sci.~ 300 ev.0.3 kton liq.sci.~ 100 ev.Giant ice 1 kton liq.sci.~ 300 ev.32 kton water ~ 8000 ev.Good directionality0.33 kton liq.sci.~ 100 ev.1 kton liq.sci.~ 300 ev.# of expected ev. for 10 kpc 4344

Pre-supernova neutrino45