Prospect for detection of supernova neutrino NOW2014 Sep. 9 th, 2014 Otranto, Lecce, Italy 森俊彰 Takaaki Mori for the Super-Kamiokande Collaboration Okayama University, Japan

Contents Supernova burst neutrinos Supernova relic neutrinos GADZOOKS! Pre-supernova neutrinos

Neutrino from supernova A supernova explosion happens when a star at least 8 times more massive than the sun collapses. Released gravitational energy: ~3x10 53 erg. Neutrinos carry almost all (99%) of the energy. Supernova neutrinos detection provides a lot of information –Collapse physics –Neutrino Physics Detection of SN neutrino is very important 2 Livermore simulation: APJ, 496, 216 (1998) Luminosity Average E

Supernova burst detectors in the world (running and near future underground experiments) Super-K KamLAND Baksan LVD Borexino SNO+ (under construction) IceCube HALO Detectors on surface like NOvA (14kton liquid scintillator(LS)), Daya Bay (160ton Gd-doped LS) can also be supernova detectors.

Super-Kamiokande 32 kton water Cherenkov detector Dominant interaction is IBD ( e +p) ( ~7300 events in total ~8000 events for 10kpc SN) –Enough statistics to discuss model predictions Good directionality for e scattering (~300 events) 4 SN monitor is running 24 hours a day Announce the SN neutrino detection and its direction to the world within an hour

IceCube 5 High statistics –0.75% stat. 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 detectors Expected number of events for 10 kpc SN Inverse beta : ~300 events/kton –Spectrum measurement with good energy resolution CC on 12 C : ~ 30 events/kton Electron scattering : ~20 events/kton NC  from 12 C : ~60 events/kton –Total neutrino flux, MeV mono energetic   + p NC : ~ 300 events/kton –Sensitive to all types of neutrinos ( Independent from neutrino osc.) 6 From K.Inoue, G.Belliini, M.Chen (Flux:PRD67, (2003))

Supernova Relic Neutrino 7

8 In the Universe, there exist SRN emitted from the past supernovae explosion Expected SRN events : 1.3~6.7 events/year/22.5kton ( MeV ) Large target mass and high background reduction are necessary Time SRN predictions ( e fluxes) Neutrino flux (/cm 2 /sec/MeV) SRN mode : PRD, 79, (2009) Neutrino Energy[ MeV]

SRN search at Super-K 9 e+e+ proton  e neutron proton 2.2 MeV  (Not efficiently detected) Search for SRN is limited by background –Need to identify neutron to suppress the atmospheric neutrino background K.Bays et al.,PRD85(2012) data ν μ CC ν e CC NC elastic μ / π > C. thr. all background SRN Energy [MeV] Super-K has the best sensitivity to the SRN via IBD interaction –flux<2.9 e (1/cm 2 /sec)

GADZOOKS! Beacom and Vagins PRL93, (2004) (Gadolinium Antineutrino Detector Zealously Outperforming Old Kamiokande, Super!) Large cross section for thermal neutron (~ 0.1 % Gd) Neutron captured Gd emits 3-4  ray in total 8 MeV 10 e+e+ proton  e neutron Gd SRN mode:PRD79,083013(2009)

SN detection w/ neutron tagging kpc Direction of SN can be determined with an accuracy of ~ 5 deg. ->By neutron tagging, direction accuracy can be improved to ~3 deg. Flux and spectrum : Livermore simulation

12 Item to study with EGADS –Effect to Water transparency –Water purification system –Neutron detection efficiency –Etc. EGADS experiment (Evaluating Gadolinium’s Action on Detector System)

13 “Selective filtration system” (Water purification system) UDEAL (Water Transparency measurement device) 200 m 3 detector (240 photo sensor) 15 m 3 tank and pre-treatment system

Current status of EGADS 14 Step1 Circulation with pure water Step2 Circulation with Gd-doped water Step3 PMT installation step 4 Circulation with pure water Detector calibration step 5 Circulation with Gd-doped water Data taking Step6 Refurbish Data analysis step 7 Circulation with Gd-doped water Evaluation of GADZOOKS! ←achieve same level pure water transparency ←achieve 86.2% of pure water cases

Current status of EGADS 15 Step1 Circulation with pure water Step2 Circulation with Gd-doped water Step3 PMT installation step 4 Circulation with pure water Detector calibration step 5 Circulation with Gd-doped water Data taking Step6 Refurbish Data analysis step 7 Circulation with Gd-doped water Evaluation of GADZOOKS!

Current status of EGADS 16 Step1 Circulation with pure water Step2 Circulation with Gd-doped water Step3 PMT installation step 4 Circulation with pure water Detector calibration step 5 Circulation with Gd-doped water Data taking Step6 Refurbish Data analysis step 7 Circulation with Gd-doped water Evaluation of GADZOOKS!

Current status of EGADS 17 Step1 Circulation with pure water Step2 Circulation with Gd-doped water Step3 PMT installation step 4 Circulation with pure water Detector calibration step 5 Circulation with Gd-doped water Data taking Step6 Refurbish Data analysis step 7 Circulation with Gd-doped water Evaluation of GADZOOKS! ←we found bad material, which is not used in SK detector

Current status of EGADS 18 Step1 Circulation with pure water Step2 Circulation with Gd-doped water Step3 PMT installation step 4 Circulation with pure water Detector calibration step 5 Circulation with Gd-doped water Data taking Step6 Refurbish Data analysis step 7 Circulation with Gd-doped water Evaluation of GADZOOKS!

Transparency of Gd-doped water 19 w/o PMT Cherenkov light left ( %)

BGO Am/Be Measurement of Gd  T[s]T[s] Total electron Energy[MeV] Events / # of prompt trg. 241 Am → 237 Np +  9 Be +  → 12 C +  (4.4MeV) + n Gd  Gate ： 500  sec Delayed signal Prompt signal Scintillation Gd 2 (SO 4 ) 3 concentration: 200 ppm

Pre-supernova neutrino detection

Pre-supernova neutrinos 22 Importance of detection –Investigation of mechanism of evolution of star at final at stage and collapse –Alarm before the SN neutrino burst Target –Antares (~170pc) –Betelgeuse (~150pc) –Gamma Velorum (~340pc) ACTA PHYSICAL POLONOCA B 40, 3063 (2009) Shell Si starts Core Si burning Direct pre- collapse stage Shock breakout SN neutrino burst Log L [erg/s] Neutrino is emitted in Si burning phase before core-collapse supernova

Pre-SN neutrino KamLAND 23 Expected number of The early alarm will be issued from 3 days to 5 hours before from core- collapse Significance Normal hierarchy Inverted hierarchy 6 /cm 2 /s/MeV) Anti e energy [ MeV ] From K.Ishidoshiro Time[day]

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 interaction A.Odrzywolek et al., AIP Conf. Proc. 944, 109 (2007)

25 Summary Supernova burst neutrinos SN neutrino provides a lot of information by energy, flavor, timing.. Many detectors are waiting a SN burst Supernova relic neutrinos R&D project for GADZOOKS! is ongoing Supernova neutrino at Si burning stage Its detection provide the very early alarm for supernova burst KamLAND and GADZOOKS! can get precursor

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S.Ando, NNN05 Supernova Relic Neutrinos S.Ando, Astrophys.J.607:20-31,2004. ~10 17 supernovae so far.

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Super-K LVD IceCube Borexino snews.bnl.gov SNEWS: SuperNova Early Warning System KamLAND Daya Bay (soon) 31

Supernova burst detectors in the world (running and near future underground experiments) Super-Kamiokande KamLAND Baksan LVD Borexino SNO+ (under construction) IceCube HALO Detectors on surface like NOvA (14kton liquid scintillator(LS)), Daya Bay (160ton Gd-doped LS) can also be supernova detectors.

Current Liquid scintillator detectors KamLAND (1kton) Borexino (0.33kton) SNO+ (1kton) under construction LVD (1kton) NO A (14kton)

alert to astronomers experiment UT time significance 10 second coincidence by UT time stamp Coincidence Server at BNL SNEWS: 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 Amateur astronomer connection snews.bnl.gov

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UDEAL 38

Pre-treat system 39

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Gd removal system 41

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Supernova burst detectors in the world (running and near future underground experiments) Super-K KamLAND Baksan LVD Borexino SNO+ (under construction) IceCube HALO 76 ton Pb, 3 He 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 directionality 0.33 kton liq.sci. ~ 100 ev. 1 kton liq.sci. ~ 300 ev. # of expected ev. for 10 kpc

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