Neutrino observatories

Transcription

1 Gravitational-wave Physics&Astronomy Workshop, January 28, 2011 Neutrino observatories M.Nakahata Kamioka observatory ICRR/IPMU, Univ. of Tokyo SN1987A

2 Contents Supernova burst neutrinos How they are produced SN1987A Current detectors in the world What information neutrino detectors can provide High energy astrophysical neutrinos How they are produced Detectors in the world

3 Core-collapse supernova Standard scenario of the core-collapse supernova Core-collapse Neutrino trapping Core bounce H He C+O Si Fe n n n n n n n Supernova burst Shock wave propagation Shock wave at core n Neutron star Figure from K.Sato n n n n

4 Neutrino emission from supernova burst Released gravitational energy: ~3x10 53 erg Neutrinos carry almost all (99%) of the energy. Energy for explosion and optical emission is only ~1%(~10 51 erg). Expected time profile Livermore simulation (x=m,t) Mean neutrino energy (x=m,t) T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998)

5 Total Binding Energy SN1987A: supernova at LMC(50kpc) Kamiokande-II IMB-3 BAKSAN Feb.23, 1987 at 7:35UT Kam-II (11 evts.) IMB-3 (8 evts.) Baksan (5 evts.) 24 events total 95 % CL Contours Theory from G.Raffelt _ Spectral n e Temperature

6 Supernova burst detectors in the world (running and near future experiments) Borexino LVD Super-Kamiokande Baksan SNO+ (under construction) HALO KamLAND IceCube

7 The Baksan underground scintillation telescope (Russia) E.N.Alexeyev, L.N.Alexeyeva, astro-ph/ Total number of standard detectors Total target mass tons of oil-based scintillator ~100 n e p e + n events expected for 10 kpc SN. Running since 1980 with ~90% live time. From E.N.Alexeyev

8 LVD detector LVD consists of an array of 840 counters, 1.5 m 3 each. Total target: 1000 t liquid scintillator 4MeV threshold With <1MeV threshold for delayed signal (neutron tagging efficiency of %) E resolution: 13%(1s) at 15MeV ~300 n e p e + n events expected for 10 kpc SN. Twenty From W.Flugione Years after SN1987A At Gran Sasso Fulgione@to.infn.it Lab., Italy

9 Single volume liquid scintillator detectors KamLAND Borexino SNO+ (Kamioka, Japan) (Gran Sasso, Italy) (SNO Lab.,Canada) 300ton liq.sci. Running since ton liq.sci. Running since ton liq.sci. Under construction. From K.Inoue, G.Bellini, M.Chen

10 Liquid scinitillator detectors Expected number of events(for 10kpc SN) Events/1000 tons Inverse beta( n e +p e + +n) : ~300 events Spectrum measurement with good energy resolution, e.g. for spectrum distortion of earth matter effect. CC on 12 C (n e + 12 C e+ 12 N( 12 B)) : Tagged by 12 N( 12 B) beta decay Electron scattering (n+e - n+e - ) : NC g from 12 C (n+ 12 C n+ 12 C+g): Total neutrino flux, 15.11MeV mono-energetic gamma n+p scattering( n+p n+p): Sensitive to all types of neutrinos. (Independent from neutrino oscillation) Spectrum measurement of higher energy component. ~30 events ~20 events ~60 events ~300 events From K.Inoue, G.Bellini, M.Chen

11 HALO - a Helium and Lead Observatory (SNO Lab., Canada) SNO 3 He neutron detectors with lead target CC: NC: HALO-1 is using an available 76 tonnes of Pb In HALO-1 for a 10kpc, Assuming FD distribution with T=8 MeV for n μ s, n τ s. 65 neutrons through n e charged current channels 20 neutrons through ν x neutral current channels ~ 85 neutrons liberated; with ~50% of detection efficiency, ~40 events expected. HALO-2 is a future kt-scale detector From C.Virtue

12 IceCube: The Giga-ton Detector Array IceTop Design Specifications (South pole) InIce AMANDA Fully digital detector concept Number of strings 75 Number of surface tanks 160 Number of Optical modules (DOMs) 4820 Instrumented volume 1 km 3 Supernova neutrinos coherently increase single rates of PMTs. Construction finished on Dec.18, From L.Koepke, S.Yoshida

13 IceCube as MeV n detector 10 kpc to SN Simulation based on Livermore model Advantage: high statistics (0.75% stat. 0.5s and 100ms bins) Good for fine time structures (noise low)! Disadvantage: no pointing no energy intrinsic noise Galactic Center IceCube Amanda LMC SMC Significance: Galactic center: ~200 s LMC : ~5 s SMC : ~4 s From L.Koepke

14 Super-Kamiokande detector (Kamioka, Japan) LINAC 41.4m Electronics hut ID OD 39.3m Water and air purification system Control room Ikeno-yama Kamioka-cho, Gifu Japan Mozumi 3km SK Atotsu entrance 1km (2700mwe) 2km Atotsu 50,000 ton water 32,000 ton photosensitive volume ~2m OD viewed by inch PMTs 32kt ID viewed by 11, inch PMTs 22.5kt fid. vol. (2m from wall) ~4.5MeV energy threshold SK-I: April 1996~ SK-IV is running

15 Super-K: Expected number of events Neutrino flux and energy spectrum from Livermore simulation (T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998)) ~7,300 n e +p events ~300 n+e events ~ O NC g events ~ O CC events (with 5MeV thr.) for 10 kpc supernova

16 Summary of current supernova n detectors # of events expected for 10kpc. Directionality Baksan (1980-) LVD (1992-) Super-K (1996-) KamLAND (2002-) ICECUBE (2005-) BOREXINO (2007-) HALO (2010-) 330 ton liquid scintillator ~100 n e p e + n events ton liquid scintillator. 840 counters 1.5m 3 each. 4 MeV thres., ~50% eff. for tagging decayed signal. ~300 n e p e + n events. 32,000 tons of water target. ~7300 n e p e + n, ~300 ne ne scattering events ton liquid scintillator, single volume. ~300 n e p, several 10 CC on 12 C, ~60 NC g, ~300 np np Gigaton ice target. By coherent increase of PMT single rates. High precision time structure measurement. 300 ton liquid scintillator, single volume. ~100 n e p, ~10 CC on 12 C, ~20 NC g, ~100 np np SNO 3 He neutron detectors with 76 ton lead target. ~40 events expected. No No Yes No No No No

17 Super-Kamiokande: Water Cherenkov detector Cherenkov light Emitted when particle travels faster than speed of light in water(c/1.33). e Emission angle = cos -1 (1/nb)=42 q Using hit PMT timing, vertex position is reconstructed. Then, direction is reconstructed using hit PMT pattern. One of the SN1987A events in Kamiokande

18 Neutrino interaction in water Cross section (H 2 O target) Angular distribution Supernova n ν+e - ν+e - ν e +p e + +n ν e + 16 O e F ν e + 16 O e N Neutrino COSq SN

19 Super-K: simulation of angular distribution n+e n+e SN at 10kpc ne+p ne+p n+e n+e ne+p ne+p Direction of supernova can be determined with an accuracy of ~5 degree. Neutrino flux and spectrum from Livermore simulation

20 Captures on Gd Future possible improvement in Super-K Identify n e p events by neutron tagging with Gadolinium. Gadolinium has large neutron capture cross section and emit 8MeV gamma cascade. n e p e + n Gd γ 100% 80% 0.1% Gd gives >90% efficiency for n capture In Super-K this means ~100 tons of water soluble GdCl 3 or Gd 2 (SO 4 ) 3 8 MeV ΔT~20μs Vertices within 50cm The main purpose of this project is to detect diffuse supernova neutrinos. 60% 40% 20% 0% % 0.001% 0.01% 0.1% 1% Gd in Water

21 Super-K: Angular distribution (with Gd) ne+p n+e ne+p n+e With n e p identification by neutron tagging ne+p n+e ne+p n+e Direction accuracy can be improved to ~3 degree. SN at 10kpc

22 Burst onset time Simulation of initial stage of a burst (10kpc supernova) Super-Kamiokande IceCube Halzen, Raffelt, arxiv: IceCube example 10~40 events in the first 20msec. ±3.5 msec at 95% C.L. Super-K and IceCube have a few msec precision on onset time.

23 Triangulation on supernova direction Beacom, Vogel, Phys.Rev.D60, , 1999 Super-K (36 N) cosq = t / d q IceCube (90 S) If Super-K and IceCube has ~2 msec rise time resolution, cos(q) = ~0.1 (i.e. about 25 deg.). Super-K resolution by electron-scattering is much better.

24 SuperNova Early Warning System snews.bnl.gov Details: arxiv:astro-ph/ Individual supernova-sensitive experiments send burst datagrams to SNEWS coincidence computer at Brookhaven National Lab(backup at U. of Bologna) alert to astronomers if coincidence in 10 seconds Participating experiments: arxiv: Super- Kamiokande (Japan) From K. Scholberg Large Volume Detector (Italy) IceCube (South Pole) SNO (Canada) until end of 2006

25 High Energy Astrophysical Neutrinos There are high energy accelerators in the universe. We know cosmic rays(p, He,..) exist. So, there much be cosmic high energy neutrinos. Possible sources: AGN, supernova remnants,. n e e + m + n m n m + g sync e - p g sync accretion disk Black hole

26 Cosmic Ultra High Energy neutrinos Ultra High Energy Cosmic Ray(UHECR) exists. Horizon of UHECR is ~50Mpc. Neutrinos galactic Extragalactic cosmic rays interact with the microwave background p g m n m } n e { e m e : n m : n t 1:1:1 GZK neutrinos m (due to n osc.)

27 Detectors for High Energy Astrophysical Neutrinos Antares Mediterranean sea 0.2x0.2x0.4km Volume: 0.01 km 3 Running since May 2008 South pole Volume:1 km 3 Construction finished in Dec.2010 NT200+ Lake Bikal 0.2 kmf 0.2 kmh Volume: 0.01 km 3 Running from 2006

28 n m only Diffuse n limit Now below the Waxman-Bahcall limit Atmospheric n IceCube Preliminary This work From S.Yoshida Sean Grullon (UW-Madison)

29 GZK n search All flavor (n e n m n t ) limits Systematic errors included IceCube Preliminary Aya Ishihara (Chiba) From S.Yoshida

30 Conclusions Supernova burst neutrinos Many detectors in the world with various types of signals. ~8,000 events expected at Super-K for 10kpc SN. High precision time profile by Icecube. ~5 deg. accuracy in direction of supernova by Super-K neutron-electron scattering events. Onset time with ~2 msec resolution by Super-K and IceCube. High energy neutrinos Construction of the IceCube was finished. High energy neutrino events are expected in near future.

31 Backups

32 Distance to Galactic supernova Mirizzi, Raffelt and Serpico, JCAP 0605,012(2006), astro-ph/ Based on birth location of neutron stars Type Ia Core collapse type mean: 10.7 kpc r.m.s.: 4.9 kpc 0 10kpc 20kpc 7% probability < 3.16 kpc > x10 statistics 16% probability < 5 kpc > x 4 statistics 3% probability > 20 kpc < 1/4 statistics

33 Super-K: Angular distribution (without Gd) ne+p n+e n+e Without n e p identification by neutron tagging ne+p n+e n+e ne+p ne+p SN at 10kpc

34 Accuracy of supernova direction with neutron tag Thomas, Sekikoz, Raffelt, Kachelriess, Dighe, hep-ph/ v2 Accuracy of SN direction with simulated supernova Tagging efficiency vs. accuracy (95% CL) Accuracy can be improved by a factor of two with neutron tagging. G: Garching model, L: Livermore model a: normal hierarchy sin 2 q 13 >10-3 b: inv. hierarchy sin 2 q 13 >10-3 c: any hierarchy sin 2 q 13 <10-3

35 COSq SN Angular distribution of ν e +p e + +n ν e +p e + + n neutrino energy 5MeV 10MeV 20MeV 30MeV A. Strumia and F. Vissani, Phys.Lett.B564:42-54,2003.

36 Super-K: Neutronization burst (e - +p n+n e ) SN at 10kpc Neutrino flux and spectrum from Livermore simulation Event rate of n e +p events Event rate of neutronization burst (forward peaked n+e scattering events) No oscillation Normal P H =1 or Inverted hierarchy Normal hierarchy P H =0 P H : crossing probability at H resonance (P H =0: adiabatic) Number of events from neutronization burst is 0.9~6 events for SN@10kpc. n e p events during this 10msec is about 8-30 events. N.H. +adiamacitc case: neutronization=0.9ev., n e p = 14 ev.(1.4 for SN direction).

37 n+p elastic signal( n+p n+p) at liq. Scintillator detectors Beacom, Farr, and Vogel, PRD66, (2002) Expected spectrum Sensitivity of temperature measurement n e n e ~300 events/kt above 200keV ~150 events/kt above 500keV Determine original n m, n m, n t, n t temperature with ~10% accuracy. (free from neutrino oscillation.) Current Borexino threshold: 200keV Current KamLAND threshold: 600~700keV(will be lowered after 2008 distillation.)