Detecting Supernova Neutrinos at Neutrino Experiments Shaomin Chen

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（ 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 2020/10/7 1

Outline n Introduction n Supernova Neutrino Signal ØSN Burst neutrinos ØSN Relic Neutrinos n SN Neutrino Interactions at Targets n Typical Neutrino Detection Methods ØIn Water and In Liquid Scintillator ØBackground sources n Status & Outlook 2020/10/7 2

INTRODUCTION 2020/10/7 3

SN 1987 a Before February 23, 1987 After February 23, 1987 First observation came from optical instruments. 2020/10/7 4

SN 1987 a Neutrino Detections 2140 -ton pure water Time accuracy 1 s Threshold: 5 Me. V 6800 -ton pure water Time accuracy 50 ms Threshold 5 Me. V w/ ¼ PMT HV off 200 -ton LS Time accuracy +2/-54 s Later confirmed by the neutrino experiments. 2020/10/7 5

2002 Nobel Prize in Physics "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" 2020/10/7 6

Puzzles in Measurements “One puzzling feature of the SN 1987 a 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. D 76 (2007) 083007 2020/10/7 7

Classification of SN Neutrinos John Beacom, TAUP 2011 DSNB=Diffuse Supernova Neutrino Background But we prefer to call them Supernova Relic Neutrinos 2020/10/7 8

SUPERNOVA NEUTRINO SIGNAL 2020/10/7 9

Model for Core-Collapse SN Stage 3, 4, 5 are expected to be distinguished by the SN neutrino time spectra. 2020/10/7 10

SN Neutrino Time Spectra 2020/10/7 11

Time Structures in N and <E> T. Totani, K. Sato, H. E. Dalhed and J. R. Wilson, Ap. J. 496, 216(1998) 1. Model based on SN 1987 a. 2. Special time structure. 2020/10/7 12

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. , ar. Xiv: 1212. 4250 2020/10/7 13

Expected SN Rate per Century SN burst neutrinos expected from Type Ib, Ic and Type II SNe. 2020/10/7 14

Galactic SN Distance Mirizzi, et al. astro-ph/0604300 If a detector is sensitive up to 20 kpc, it covers 97% of our galaxy. Core collapse type Type Ia 0 7% probability < 3. 16 kpc 2020/10/7 10 kpc 16% probability < 5 kpc mean: 10. 7 kpc r. m. s. : 4. 9 kpc 20 kpc 3% probability > 20 kpc 15

Candidate SN Close to Us Eta Carinae： 2. 3 kpc to the Earth (SN 1987 a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. 2 kpc 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. 2020/10/7 SN 1987 a 16

Supernova Relic Neutrinos 2020/10/7 17

SRN @ SK 2020/10/7 18

SN NEUTRINO INTERACTIONS AT TARGETS 2020/10/7 19

SN Neutrino Interactions in Use 1. Inverse Beta Decay 2. Elastic Scattering On Electrons 3. CC and NC Interactions With Nuclei 4. Coherent Elastic Neutrino-Nucleus Scattering 2020/10/7 20

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TYPICAL NEUTRINO DETECTION METHOD 2020/10/7 22

Detection in Water ne n p e+ 2020/10/7 p Gd g g 23

Particle ID at SK If +/ – is fully contained in the inner tank Cone vertex and # of PMT and total charge collected used for measuring Evis 2020/10/7 If e+/e– is fully contained in the inner tank Ring pattern diff. used for PID 24

Detection in Liquid Scintillator e n e t e+ n 2020/10/7 Ø A prompt event correlated with a delayed event Ø Isotropic scintillation light Ø Typical a 8 Me. V gamma cascade and a 2. 2 Me. V gamma 25

Summary of SN Experiments 2020/10/7 26

Background in SN Burst Neutrinos Signal 2020/10/7 Background 27

Spallation Background 2020/10/7 28

Background Sources in SRN 2020/10/7 29

STATUS AND OUTLOOK 2020/10/7 30

Expected SN Neutrino Events Kamioande 参宿四 （0. 2 kpc） Daya Bay 海山二 （2. 3 kpc） 1987 a （51. 4 kpc） 31 2020/10/7

Super. Nova 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: Super. Kamiokande (Japan) 2020/10/7 Large Volume Detector (Italy) AMANDA/ Ice. Cube (South Pole) SNO (Canada) until end of 2006 32

Approaches @ SK ne Forced Trigger n p p g n+p→d + g 2. 2 Me. V g-ray DT = ~ 200 sec # of hit PMT’s ~ 6 e+ Gd (S. Chen and Z. Deng) g Nucl. Phys. Proc. Suppl. 166: 252, 2006 GADZOOKS! n+Gd →~8 Me. V g’s DT = ~30 sec Add 0. 2% Gd. Cl 3 in (J. Beacom and M. Vagins) water Phys. Rev. Lett. 93: 171101, 2004 2020/10/7 ne can be identified by delayed coincidence. 33

Water with 0. 2% Gd. Cl 3 Solution 5 cm Am/Be α + 9 Be → 12 C* + n 12 C* → 12 C + (4. 4 Me. V) n + p → …… → n + Gd → Gd + (totally 8 Me. V) 2020/10/7 34

The 8 Me. V Gamma Cascade @SK Efficiency ~ 67% Background probability ~ 2 x 10 -4 Distance to positron [cm] 2020/10/7 35

The 2. 2 Me. V Gamma @ SK 2020/10/7 36

Efficiency & BKG Prob. Efficiency ~ 18% Background probability ~ 1 x 10 -2 2020/10/7 37

2. 2 Me. V Gamma in Neutrino Data 2020/10/7 38

A First Look Into SK-IV Data SK-I Kam. Land SK-IV SK-I+II+III 2020/10/7 39

Prospect of SRN at SK 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 Me. V) 2020/10/7 40

SN Burst Neutrinos @Daya. Bay 4 x(20+20)+2 x(20+20)+ 2 x(20+20)=320 tons Three-hall configuration can significantly reduce false SN alarming by the spallation background 2020/10/7 41

SN Neutrinos at Daya. Bay-II DYB 2020/10/7 DYB II 20 k ton LS 42

Status Power 阳江 Under construction 17. 4 GW 台山 Under construction 18. 4 GW 43 2020/10/7

Outlook u Many Physics in SN Neutrinos ü Dynamics of Core-Collapse SN, Mass Hierarchy ü Star Formation History, … u Rare SN burst neutrinos but copious SRNs u Need large volume of target mass with advanced detection technologies u A more realistic outlook ü SK with Gd+H and Daya Bay II 2020/10/7 44

THANKS! 2020/10/7 45