Supernova neutrinos in SK-Gd and other experiments€¦ · Pre-supernova at 200pc Hiroyuki Sekiya...
Transcript of Supernova neutrinos in SK-Gd and other experiments€¦ · Pre-supernova at 200pc Hiroyuki Sekiya...
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
tSupernova neutrinos in SK-Gd
and other experimentsNEUTRINO2016 @LONDON
JULY 9 2016
Hiroyuki SekiyaICRR, University of Tokyo
for the Super-K Collaboration
Total 24 pages
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Supernova neutrinos from 1987A The only detected SN neutrinos are from LMC(50kpc)
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Kamiokande-II (11 evts.)IMB-3 (8 evts.)Baksan (5 evts.)
Jegerlehner, Neubig & Raffelt, PRD 54 (1996) 1194
Total energy
released by ν̅e: ~5x1052 erg
24 (ν̅e ) events in total.
The obtained binding energy is almost as expected, but large error in neutrino mean energy. No detailed information of burst process.
We need energy, flavor and time structure.
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Many models… Need data!Figures: H.Suzuki, M. Nakahata
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“Livermore”as a reference
“Nakazato”as a reference
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Detectors that observed 1987A
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Kamiokande-II◦ 2140 ton FV◦ Water Cherenkov◦ > 8.5MeV
Essentially, inverse beta decay events.
BAKSAN◦ Total 330ton ◦ Liquid Scintillator◦ > 10 MeV
IMB-3◦ ~5000 ton FV◦ Water Cherenkov◦ > 28 MeV
SNOwGLoBES http://www.phy.duke.edu/~schol/snowglobes/
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
The current water detector Super-Kamiokande
◦ 32k ton FV > 4.5 MeV(kin)◦ 8.8k ton FV > 3.5MeV(kin)
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Livermore Nakazatoν̅ep e+n 7300 3100ν+e- ν+e- 320 17016O CC 110 57
Supernova at 10 kpc# events in 32kton SK volume
Pointing accuracy ~5°
Livermore: ApJ.496,216(1998)Nakazato: ApJ.Suppl. 205 (2013) 2
Angular distributions
May help large optical telescopes.
20Msun, trev=200msec, z=0.02
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Water detectors provide high statistics
ICECUBE◦ Giga-ton◦ By increase of PMT single rates, fine
time structure is obtained.
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Time variation of mean energyTime variation of event rate
IceCube collaboration,A&A 535, A109 (2011)
Super-Kamiokande (cont’d)
Enough statistics to discriminate models!Supernova at 10 kpc
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Current liquid scintillators KamLAND
◦ 1kton
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LVD◦ 1kton
Borexino◦ 320 ton
NOvA◦ 14k ton
BAKSAN◦ 330 ton
Daya bay◦ 20 ton x 8 (SNO+)
◦ 1k ton
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Liquid scintillators KamLAND
◦ Low threshold o(100keV)◦ Sensitive to Si burning phase. KamLAND send pre-SN alarm <700pc
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Livermore
νe̅p e+n 300
ν+e- ν+e- 20
ν+p ν+p 30012C CC 60
Pre-SN ν
Reactor ν
Geo-ν
Time evolution Odrzywolek 2010, Nakazato 2012
Pre-SN
Supernova at 10 kpc
SN, t=0
IshidoshiroPre-supernova at 200pc
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Kate Scholberg Neutrino2014
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Supernova-relevant neutrino interactionsElectrons Protons Nuclei
Chargedcurrent
Elastic scattering
Usefulfor pointing
Inverse beta decay
Neutralcurrent
Elasticscattering
γ
γe+
nνe
γ
ν
e-
νe
e-e+/-
νe
γ n
γVarious possibleejecta anddeexcitationproducts
Coherentelastic (CEνNS)
νγ n
γν
Aνp
very low energyrecoils
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Nuclei targets HALO
◦ 79 t of Lead◦ SNO’s 3He counter◦ polypropylene tubes for n moderation
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reaction neutrons
CC 1n 30
CC 2n 19x2
NC 1n 8
NC 2n 6x2
n + 3He → 3H + p + 764 keVNot sensitive to e-, no NC/CC discrimination
νe + 208Pb → 207Bi + n + e-
νe + 208Pb → 206Bi + 2n + e-
νx + 208Pb → 207Pb + nνx + 208Pb → 206Pb + 2n
CC NC ES
Supernova at 10 kpcA Habig
~50% of detection efficiency~40 events are expected
(ICARUS) ◦ Ar-TPC 600t ◦ LGNS→FNAL
νe + 40Ar → 40K* + e-
ν̅e + 40Ar → 40Cl* + e+
νx + 40Ar → νx + 40Ar* νx + e- → νx + e-
Livermore
νe + 40Ar 40
ν̅e + 40Ar 3
νx + e- 5
Supernova at 10 kpc
Unique sensitivity to νe
Possibility to separate channels by the associated deexcitation
Scaled from Inés Gil-Botella’s DUNE value
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
DM detectors Coherent elastic neutrino-nucleus scattering
LUX◦ Xe 0.37 ton FV
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XMASS◦ Xe 0.83 ton FV in 800t water◦ >300eV◦ SK GPS ◦ KamLAND
Pre-alarm
Xe
CEνNS cross section
Ar
P. C. Divari High Energy Phys. (2012) 379460
Supernova at 10 kpc
CEνNSev
ents
/10s
ec
XMASS BGSupernova at 200 pc
Livermore
ν+Xe ν+Xe 15
Livermore
ν+Xe ν+Xe 3.9x104
(DEAP3600)◦ Ar 3.6 ton FV
XENON1T◦ Xe 1 ton FV
K. Hiraide
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Super-KamiondeEGADSKamLAND-ZenXMASS
LVDBorexinoXENON1T
Baksan
IceCube
DayaBay
NOvA
SNO+HALODEAP3600
LUX
Supernova neutrino detectors
Antares
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Larger detectors in future
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DUNE◦ 40kton Ar TPC
IceCube-Gen2/PINGUKM3NeT Phase-2.0/ORCA
JUNO / RENO50◦ Liq. Sci ~20kton
Tamborra et al.,PRD 90 045032 (2014)
Supernova at 10 kpcSASI observation!
Supernova rate based on 2000-2011Horiuchi et al., ApJ. 769 (2013) 113
Hyper-K 0.38MtonDetection Probability
Hyper-Kamiokande◦ 0.5 Mton, 0.38 Mton FV◦ 0.2~3.3 SNe in 10 years(N>2)
Extend detection reach to 10 Mpc!
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Extend to whole universe… DSNB (SRN) 1010 stellar/galaxy ×1010 galaxies ×0.3%(become SNe) ~O(1017)SNe
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Beginning of the universe
NOW
1billion years ago
10 billion years ago
Neutrinosfrom past SNe
Horiuchi, Beacom and Dwek, PRD, 79, 083013 (2009)
Search window for SK : From ~10MeV to ~30MeV
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Status of DSNB search
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Comparison with expected ν̅e signal
Limited by BG. More than 1 order reduction is needed.◦ n tagging efficiency (by proton) is low…
Theoretical flux prediction : 0.3~1.5 /cm2/sCurrent best limit by SK: 2.8~3.1 /cm2/s
(>17.3MeV)
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
SK-Gd project Identify νep events by neutron tagging with Gadolinium. Large cross section for thermal neutron (48.89kb) Neutron captured Gd emits 3-4 γs in total 8 MeV Gd2(SO4)3 was selected to dissolve.
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Beacom and Vagins PRL93,171101 (2004)
Cap
ture
s on
Gd
Gd in Water
100%
80%
60%
40%
20%
0.0001%0.001% 0.01% 0.1% 1%
0.1% Gd (0.2% in Gd2(SO4)3) gives~90% efficiencyfor n capture
0%
In Super-K this requires dissolving ~100 tonsof Gd2(SO4)3
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
BG source: atmospheric neutrino CC
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Invisible μ n + decay-e
(anti-)νe CC
μ generation
νe e
νμ μ eT < 50 MeV
“invisible muon”
νμ μ
n
n
n
NCNC elastic de-excitation γ
νx νx
16O* → γn
Total energy MeVN.B. Vertex information gives further BG reduction
even
ts/y
ear/
1.5M
eV
Expected BG rate
νe CCνµ CC
NC elastic
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Expected signal
It depends on typical/actual SN emission spectrum
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Total (positron) energy MeV
even
ts/y
ear/
1.5M
eV
DSNB flux:Horiuchi, Beacom and Dwek, PRD, 79, 083013 (2009)
Expected total BGTν = 6MeVTν = 4MeVTν = 1987a
HBDmodels
10-16MeV(evts/10yrs)
16-28MeV(evts/10yrs)
Total(10-28MeV)
significance(2 energy bin)
Teff 8MeV 11.3 19.9 31.2 5.3 σ
Teff 6MeV 11.3 13.5 24.8 4.3 σ
Teff 4MeV 7.7 4.8 12.5 2.5 σ
Teff SN1987a 5.1 6.8 11.9 2.1 σ
BG 10 24 34 ----
First observation is within SK-Gd’s reach!
DSNB events number with 10 years observation
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Not only for DSNB
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ν̅e+p
ν+e scattering
(10kpc SN simulation)
ν+e-→ν+e-ν̅e +p→e++n
If ν̅e can be tagged, directional events (ν+e scattering events) are enhanced. Pointing accuracy should be improved. For 10kpc SN ~5° ~3°(@90%C.L.)
ν̅e w/o tagging ν̅e tagged with 80% eff.
Sensitive to ν̅e of Si burning phase. 800~2000 events/day for pre-supernova at 200pc
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
EGADS To study the Gd water quality with actual detector materials. The detector fully mimic Super-K detector;
SUS frame, PMT and PMT case, black sheets, etc. Tests for Hyper-K; 13 HPDs
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Evaluating Gadolinium’s Action on Detector Systems200 m3 tank with 240 PMTs
15m3 tank to dissolve Gd
Gd water circulation system(purify water with keeping Gd)
EGADS2014
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Water transparency and Gd concentration in EGADS
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Gd had been dissolved from Nov. 2014 to May. 2015
Pure water
The light left at 15 m in the 200m3
tank was very stable and ~75% for 0.2% Gd2(SO4)3 , which corresponds to ~92% of SK-IV pure water average.
Reached target value in 2015 Apr.
Gd2(SO4)3 concentration is uniform and stable.
Sampling positionTopCenterBottom
2000
1500
1000
500Con
cent
ratio
n(pp
m)
Che
renk
ov li
ght
left
at
15 m
(%
)
Blue band: SK-III and SK-IV values
2014 2015
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
SK & T2K Joint Statement on “SK-Gd”
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On June 27, 2015, the Super-Kamiokande collaboration approved the SK-Gd project which will enhance neutrino detectability by dissolving gadolinium in the Super-K water.T2K and SK will jointly develop a protocol to make the decision about when to trigger the SK-Gd project, taking into account the needs of both experiments, including preparation for the refurbishment of the SK tank and readiness of the SK-Gd project, and the T2K schedule including the J-PARC MR power upgrade. Given the currently anticipated schedules, the expected time of the refurbishment is 2018.
Jan.30, 2016
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
New water system is under construction
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Current main water system
New Gd water purification system
SK
2016 Apr. 8mx7mx50m
will be in FY2016
Ordered dissolving system and 60t/h circulation system
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Conclusion
Only SN1987A so far. Many detectors in the world are waiting for next SN. SK-Gd project tries to catch neutrinos from past SNe. 0.2% of Gd sulfate was dissolved in EGADS test tank and
it was confirmed that there is no showstopper for putting Gd into SK, therefore SK-Gd was accepted by Super-K collaboration in June 2015.
SK & T2K joint statement was made in Jan. 2016 and the SK refurbishment in 2018 is anticipated.
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We will change! SK evolves into SK-Gd.
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Extra slides
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Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Relevant processes
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SNOwGLoBES http://www.phy.duke.edu/~schol/snowglobes/
IBD dominates. <20MeV, electron elastic scatterings can be used.
Water detectors Liquid scintillators
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Detectors ready for Supernova
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Online since
Detector#of events expected for 10kpc SN
Directionality
Baksan 1980 330 ton liquid scintillator ~100 ν̅ep e+n No
LVD 1992 1000 ton liquid scintillator, 840 counters. ~300 ν̅ep e+n No
Super-K 1996 32,000 tons of water target.~7300 ν̅ep e+n, ~300 νeνe
Yes
KamLAND 2002 1000 ton liquid scintillator, single volume. ~300 ν̅ep , ~60 CC on 12C, ~300 νp νp
No
ICECUBE 2005 Gigaton ice target.By coherent increase of PMT single rates.
No
BOREXINO 2007 300 ton liquid scintillator, single volume. ~100 ν̅ep , ~20 CC on 12C, ~100 νp νp
No
HALO 2010 SNO 3He neutron detectors with 76 ton lead target. ~40 No
Daya Bay 2011 20ton x 8, total 160ton liquid scintillator, ~50 ν̅ep No
NOvA 2014 Surface detector. 14kton liquid scintillator. No
Hiroyuki Sekiya NEUTRINO2016 London July 9 2016
Neutron capture signal in EGADS Using Am/Be + BGO
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[μsec]
Gd concentration dependence was confirmed.
Delayed signal spectrum
DataMC
Time to delayed signal
DataMC