Supernova Neutrino Detectors: Current and Future. Kate Scholberg, Duke University June 24, 2005

Transcription

1 Supernova Neutrino Detectors: Current and Future Kate Scholberg, Duke University June 24, 2005

2 OUTLINE Supernovae and the Neutrino Signal What We Will Learn Supernova Neutrino Detection Current SN ν Detectors Future SN ν Detectors Summary

3 The Supernova Neutrino Signal Gravitational binding energy of proto-nstar: < 1% of binding energy in em radiation, kinetic energy; 99% in ν's of all flavors (Energy can escape via ν's)

4 "Breakout peak": 1% of total signal is at outset energy M. Liebendorfer et al. luminosity ν µ,τ 1 s

5 Summary of the Expected Neutrino Signal Neutrinos of all flavors, roughly equal luminosity per flavor Robust flavor-energy hierarchy Energies: <E > ~ 12 MeV <E > ~ 15 MeV ( ) <Eν µ,τ > ~ 18 MeV Fewer interactions w/ proto-nstar deeper ν-sphere hotter ν's Timescale: prompt after core collapse t~10's of seconds (possible sharp cutoff if BH forms) Overall, can expect 3±1 per century

6 SN1987A Type II in LMC (~55 kpc) Water Cherenkov: IMB E th ~ 29 MeV, 6 kton 8 events Kam II E th ~ 8.5 MeV, 2.4 kton 11 events Liquid Scintillator: Baksan E th ~ 10 MeV, 130 ton 3-5 events Mont Blanc E th ~ 7 MeV, 90 ton 5 events?? 50.0 Energy (MeV) Kamiokande II IMB Time (seconds) Confirmed baseline model... but still many questions

7 What Can We Learn from a Galactic Supernova Neutrino Signal? NEUTRINO PHYSICS ν absolute mass from time of flight delay MNS parameters from spectra (flavor conversion in supernova matter, in Earth) CORE COLLAPSE PHYSICS explosion mechanism proto nstar cooling, quark matter black hole formation ASTRONOMY FROM EARLY ALERT from flavor, energy, time structure of burst ~hours of warning before visible SN, + some pointing with ν's progenitor and environment info unknown early effects?

8 Remaining Questions What is the absolute mass scale? What is the mass hierarchy? m 23 2 m 12 2 { { µ e µ e µ τ τ or What is U e3? Is it non-zero? τ (that supernova neutrinos might shed light on) (Best from SN: ~ few ev... not better than lab) "Normal" hierarchy (atm.) (solar) "Inverted" hierarchy { 2 m 12 { 2 m 23 e e µ µ µ τ τ τ

9 Perhaps most promising: Neutrino Oscillations, Mass Hierarchy e.g. Fuller et al. astro-ph/ , Dighe et al. hep-ph/ , Lunardini et al. hep-ph/ Barger et al. hep-ph/ , Minakata et al. hep-ph/ etc. Energies: <E > ~ 12 MeV <E > ~ 15 MeV ( ) <Eν µ,τ > ~ 18 MeV Flavor-energy hierarchy is robust Flavor transformations in stellar matter spectral distortion e.g. expect hot or Also: matter effects in Earth can modify signal compare NC,, rates and spectra

10 CORE COLLAPSE PHYSICS Learn about: 'Signatures': accretion explosion rotation convection, hydrodamic instabilities proto n-star EOS, strange matter black hole formation risetime breakout pulsation cooling luminosity cutoff Measure: flavor energy time structure of ν burst feedback to neutrino physics

11 Supernova Neutrino Detectors Need ~ 1kton for ~100 interactions Must have bg rate << rate in burst Also want: Timing Energy resolution Pointing Flavor sensitivity (neutral current) Sensitivity to different flavors and ability to tag them is key! vs vs ν x

12 SCINTILLATION DETECTORS Liquid scintillator C n H 2n volume surrounded by photomultipliers Mont Blanc, Palo Verde, Chooz, MACRO, Baksan, LVD Borexino, KamLAND, BooNE Inverse Beta Decay (CC) NC Excitation of 12 C (NC) Elastic Scattering (CC,NC) + p e + + n ν x + 12 C ν x + 12 C* ν x + e - ν x + e - ~5% ~few % Proton Scattering (NC) ν x + p ν x + p J. Beacom et al., hep-ph/ Very little pointing capability low energy

13 Examples of scintillation detectors KamLAND (Japan) Borexino 1 kton ~300 at 8.5 kpc (Italy) 0.3 kton ~100 LVD (Italy) 1 kton ~200 Mini-BooNE (Fermilab) 0.7 kton ~200 (detector on surface!)

14 WATER CHERENKOV DETECTORS Also: CC on oxygen + 16,18 O 16,18 F + e - Volume of clear water viewed by PMTs IMB, Kam II, Super-K, part of SNO Inverse Beta Decay (CC) + p e + + n NC on oxygen + 16 O 16 N + e + ν x + 16 O ν x + 16 O* Still dominates Elastic Scattering (CC,NC) ν x + e - ν x + e - ~few % POINTING from Ch cone δθ~25 o /n 1/2

15 Example: Super-Kamiokande Mozumi, Japan 50 kton of water (32 kton inner + outer detector) - SK II (47% ID PMTs) now operating - full reconstruction Oct 2005-Mar 2006 Events expected for collapse at 8.5 kpc, > 5 MeV: + p e + + n ν x + 16 O ν x + 16 O* + 16,18 O 16,18 F + e O 16 N + e ν x + e - ν x + e (5-10 from breakout) Pointing: ~4 o at 8.5 kpc

16 Possible enhancement: ~0.2% gadolinium trichloride in water Beacom & Vagins hep-ph/ p e + + n R&D underway capture neutron to tag (8 MeV of γ's)

17 HEAVY WATER DETECTORS D 2 O viewed by PMTs plus n detection SNO CC breakup + d p + p + e - + d n + n + e + NC breakup ν x + d n + p + ν x ν x + d n + p + ν x Very good flavor sensitivity from NC, some pointing

18 Example: Sudbury Neutrino Observatory 1.7 kton H 2 O 1 kton D 2 O Cherenkov light from e - Neutron detection: capture on d (capture on Cl) neutron detectors Events expected for collapse at 8.5 kpc: + p e + + n ν x + e - ν x + e - + d p + p + e ν Pointing: ~15 deg e + d n + n + e ν at 8.5 kpc x + d n + p + ν x 400

19 LONG STRING WATER CHERENKOV DETECTORS ~km long strings of PMTs in very clear water or ice AMANDA, Antares Baikal, NESTOR Nominally multi-gev energy threshold But, may see burst of low energy 's as coincident increase in single PMT count rates (M eff ~ 0.4 kton/pmt)

20 Example: AMANDA at the South Pole (and successor Ice-Cube) Collapse at 8.5 kpc 16 σ excess over bg counting rate Special SN trigger installed

21 'High Z' Detectors NC CC{ Liquid Argon ν x + (A,Z) (A-1,Z) + n + + (A,Z) (A-1,Z+1) + n + e - + (A,Z) (A-1,Z-1) + n + e + Large quantity of Pb (ClO 4 ) 2, Fe + scintillator, n counters OMNIS, ADONIS CC + 40 Ar e K* Icarus, LANNDD Radiochemical Chlorine Gallium + 37 Cl e Ar + 71 Ga e Ge plus 35 Cl, 12 C NC, CC? (quasi) real-time? Plus: gravitational radiation? (from asymmetric collapse)

22 Neutrino-Nucleus Elastic Scattering in Ultra-Low Energy Detectors High x-scn but low recoil energy (10's of kev) possibly observable in solar pp/dm detectors NC sensitive to all flavors ~few events per ton at 10 kpc! spectral information ν x e.g. CLEAN, DEAP, XENON Horowitz et al., astro-ph/

23 Summary of Types of SN Neutrino Detectors Primary sensitivity is to, NC for heavy water, high Z Pointing for water Cherenkov, heavy water, argon All real-time except radiochemical All have energy resolution except long string, radiochemical

24 Summary of Current SN Neutrino Detectors ± 50% ~ Galactic sensitivity

25 FUTURE DETECTORS Want: Statistics! Some possibilities: High Z: OMNIS Timing Energy resolution Pointing Flavor sensitivity (neutral current) m limit α N -1/4, pointing α N -1/2, but stats needed for osc and core collapse physics! Plus, want extragalactic sensitivity Large Water Cherenkov: UNO, Hyper-K Large Liquid Argon: LANNDD Large Liquid Scintillator: LENA, HSD Piggyback on long baseline, e.g. NOνA DEDICATED Not dedicated, but good SN capability

26 OMNIS/ADONIS: Observatory for Multiflavor Neutrino Interactions from Supernovae Dedicated supernova ν detector Pb (as metal and/or perchlorate) (and/or Fe) scint, n detectors Pb 208 Bi* + e - CC 1n, 2n emission ν x Pb 208 Pb* + ν x NC 1n, γ emission Relative rates depend on nergy => good flavor oscillation sensitivity

27 LARGE WATER CHERENKOV DETECTORS proton decay, long baseline ν oscillation UNO: Underground Nucleon Decay and Neutrino Observatory In 400 kton f.v., expect: ~130,000 inv. beta decay, 4500 NC, 4500 ES (<1 o pointing), ~dozen from Andromeda Hyper-K (Japan) 1 Mton Just scale by mass

28 LANNDD Liquid Argon Neutrino and Nucleon Decay Detector proton decay, solar, long baseline 70 kton magnetized liquid argon TPC ~6000 SN events, more if oscillations

29 Future scintillator detectors SNO+: kiloton scale Huge detectors: LENA (Europe) or, HSD in the US ~100 kton scale >10,000 SN events

30 Large surface long baseline detectors may even have manageable background during a supernova burst

31 Distance sensitivity (kpc) Distance for 90% CL detection, 1/month threshold Andromeda λ= Hz/kton λ=0.001 Hz/kton Distance sensitivity for alert depends on: Mass Background rate λ LMC Far side of Galaxy λ=0.01 Hz/kton Detector Mass (kton) E th ~ 5 MeV T = 10 s

32 Current and Future SN Neutrino Detectors extra } galactic

33 SNS Stopped Pion neutrino beam is ideal for measuring cross-sections/ calibrating detectors (see Y. Efremenko talk) Neutrino Flux ν µ ν µ Energy, M ev

34 SUMMARY A core collapse will yield a vast quantity of info! Neutrino physics (mass hierarchy, θ 13!!) Core collapse physics Early alert for astronomers (SNEWS) Several supernova neutrino detectors with Galactic sensitivity are online now (or soon) Super-K, SNO, LVD, AMANDA, KamLAND, Borexino, Mini-BooNE,... The Next Generation: perhaps extragalactic sensitivity OMNIS, UNO, Hyper-K, LANNDD, HSD, LENA... Sensitivity to different flavors and ability to tag them is key! vs vs ν x