Detecting Supernova Neutrinos at Neutrino Experiments Shaomin Chen (陈少敏) Center for High Energy Physics (高能物理研究中心) Department of Engineering Physics（工程物理系） Tsinghua University (北京清华大学) 2013年兩岸粒子物理與宇宙學研討會 2019/4/28

Outline Introduction Supernova Neutrino Signal SN Burst neutrinos SN Relic Neutrinos SN Neutrino Interactions at Targets Typical Neutrino Detection Methods In Water and In Liquid Scintillator Background sources Status & Outlook 2019/4/28

Introduction 2019/4/28

SN1987a First observation came from optical instruments. Before February 23, 1987 After February 23, 1987 First observation came from optical instruments. 2019/4/28

SN1987a Neutrino Detections 2140-ton pure water Time accuracy  1 s Threshold: 5 MeV 6800-ton pure water Time accuracy  50ms Threshold 5 MeV w/ ¼ PMT HV off 200-ton LS Time accuracy +2/-54 s Later confirmed by the neutrino experiments. 2019/4/28

2002 Nobel Prize in Physics "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" 2019/4/28

Puzzles in Measurements “One puzzling feature of the SN 1987a data is that the neutrinos detected by the IMB detector were seemingly more energetic than those detected by the Kam-II detector, which were clustered at low energies.” Phys.Rev. D76 (2007) 083007 2019/4/28

Classification of SN Neutrinos John Beacom, TAUP2011 DSNB=Diffuse Supernova Neutrino Background But we prefer to call them Supernova Relic Neutrinos 2019/4/28

Supernova Neutrino Signal 2019/4/28

Model for Core-Collapse SN Stage 3, 4, 5 are expected to be distinguished by the SN neutrino time spectra. 2019/4/28

SN Neutrino Time Spectra 2019/4/28

Time Structures in N and <E> T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998) Model based on SN1987a. Special time structure. 2019/4/28

SN Neutrinos As Probes of MH The original flavor at emission arriving at a detector on Earth depends on the neutrino mass hierarchy. C.D. Ott, et al., arXiv:1212.4250 2019/4/28

Expected SN Rate per Century SN burst neutrinos expected from Type Ib, Ic and Type II SNe. 2019/4/28

Galactic SN Distance Mirizzi, et al. astro-ph/0604300 If a detector is sensitive up to 20kpc, it covers 97% of our galaxy. Core collapse type mean: 10.7 kpc r.m.s.: 4.9 kpc 16% probability < 5 kpc Type Ia 7% probability < 3.16 kpc 3% probability > 20 kpc 10kpc 20kpc 2019/4/28

Candidate SN Close to Us Eta Carinae：2.3kpc to the Earth (SN1987a为52±5 kpc),with a mass equivalent to 100-150 Suns. Near the same bright as normal SNs, predicted to be the next SN or Hyper SN. Betelgeuse： 0.2kpc to the earth, with a Mass equivalent to 18-19 Suns. The brightest one in the sky if our eyes can see all the wavelength. SN1987a 2019/4/28

Supernova Relic Neutrinos 2019/4/28

SRN @ SK 2019/4/28

SN Neutrino Interactions at Targets 2019/4/28

SN Neutrino Interactions in Use Inverse Beta Decay Elastic Scattering On Electrons CC and NC Interactions With Nuclei Coherent Elastic Neutrino-Nucleus Scattering 2019/4/28

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Typical Neutrino Detection Method 2019/4/28

Detection in Water n g ne p p Gd e+ g 2019/4/28

Particle ID at SK Ring pattern diff. used for PID If +/– is fully contained in the inner tank Cone vertex and # of PMT and total charge collected used for measuring Evis Ring pattern diff. used for PID If e+/e– is fully contained in the inner tank 2019/4/28

Detection in Liquid Scintillator  n n e t A prompt event correlated with a delayed event Isotropic scintillation light Typical a 8 MeV gamma cascade and a 2.2 MeV gamma 2019/4/28

Summary of SN Experiments 2019/4/28

Background in SN Burst Neutrinos Signal Background 2019/4/28

Spallation Background 2019/4/28

Background Sources in SRN 2019/4/28

Status and outlook 2019/4/28

Expected SN Neutrino Events Kamioande Daya Bay 参宿四 （0.2kpc） 海山二 （2.3kpc） 1987a （51.4kpc） 2019/4/28

SuperNova Early Warning System Individual SN-sensitive experiments send burst datagram to SNEWS coincidence computer at BNL to alert astronomers if coincidence in 10 s Participating experiments: Large Volume Detector (Italy) Super- Kamiokande (Japan) AMANDA/ IceCube (South Pole) SNO (Canada) until end of 2006 2019/4/28

(S. Chen and Z.Deng) Nucl. Phys. Proc. Suppl. 166:252,2006 Approaches @ SK 2.2MeV g-ray DT = ~ 200 msec Forced Trigger n+p→d + g # of hit PMT’s ~ 6 n g ne p p Gd (S. Chen and Z.Deng) Nucl. Phys. Proc. Suppl. 166:252,2006 e+ g n+Gd →~8MeV g’s DT = ~30 msec GADZOOKS! (J.Beacom and M.Vagins) Phys.Rev.Lett.93:171101,2004 Add 0.2% GdCl3 in water ne can be identified by delayed coincidence. 2019/4/28

Water with 0.2% GdCl3 Solution 5 cm Am/Be α + 9Be → 12C* + n 12C* → 12C + g(4.4 MeV) n + p → …… → n + Gd → Gd + g (totally 8 MeV) 2019/4/28

The 8 MeV Gamma Cascade @SK Efficiency ~ 67% Background probability ~ 2 x 10-4 Distance to positron [cm] 2019/4/28

The 2.2 MeV Gamma @ SK 2019/4/28

Efficiency & BKG Prob. Efficiency ~ 18% Background probability ~ 1 x 10-2 2019/4/28

2.2 MeV Gamma in Neutrino Data 2019/4/28

A First Look Into SK-IV Data KamLand SK-IV SK-I+II+III 2019/4/28

Prospect of SRN at SK Assuming ~70% efficiency. By 10 yrs SK data, Assuming invisible muon B.G. can be reduced by a factor of 5 by neutron tagging. Assuming ~70% efficiency. By 10 yrs SK data, Signal: 33, B.G. 27 (Evis =10-30 MeV) 2019/4/28

SN Burst Neutrinos @DayaBay 4x(20+20)+2x(20+20)+ 2x(20+20)=320 tons Three-hall configuration can significantly reduce false SN alarming by the spallation background 2019/4/28

SN Neutrinos at DayaBay-II 20k ton LS DYB DYB II 2019/4/28

阳江 台山 Status Under construction Power 17.4 GW 18.4 GW 2019/4/28

Outlook Many Physics in SN Neutrinos Dynamics of Core-Collapse SN, Mass Hierarchy Star Formation History, … Rare SN burst neutrinos but copious SRNs Need large volume of target mass with advanced detection technologies A more realistic outlook SK with Gd+H and Daya Bay II 2019/4/28

THANKS! 2019/4/28