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

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

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

Neutrino emission from supernova burst Livermore simulation T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998) 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 Mean neutrino energy (x= 

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

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

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

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

Single volume liquid scintillator detectors KamLANDBorexinoSNO+ 1000ton liq.sci. Running since ton liq.sci. Running since ton liq.sci. Under construction. (Kamioka, Japan)(Gran Sasso, Italy)(SNO Lab.,Canada) From K.Inoue, G.Bellini, M.Chen

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

HALO - a Helium and Lead Observatory HALO-1 is using an available 76 tonnes of Pb CC: NC: SNO 3 He neutron detectors with lead target In HALO-1 for a 10kpc †, Assuming FD distribution with T=8 MeV for μ ’s, τ ’s. 65 neutrons through 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 (SNO Lab., Canada) From C.Virtue

IceCube: The Giga-ton Detector Array Fully digital detector concept Number of strings – 75 Number of surface tanks – 160 Number of Optical modules (DOMs) – 4820 Instrumented volume – 1 km 3 Design Specifications Construction finished on Dec.18, IceTop InIce AMANDA Supernova neutrinos coherently increase single rates of PMTs. (South pole) From L.Koepke, S.Yoshida 1450m 2450m

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 IceCube as MeV detector 10 kpc to SN LMC Galactic Center SMC IceCube Amanda Significance: Galactic center: ~200  LMC : ~5  SMC : ~4  From L.Koepke

Super-Kamiokande detector 50,000 ton water 32,000 ton photo- sensitive 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 Electronics hutLINAC Control room Water and air purification system SK 2km3km 1km (2700mwe) 39.3m 41.4m Atotsu entrance Atotsu Mozumi Ikeno-yama Kamioka-cho, Gifu Japan ID OD (Kamioka, Japan)

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

Summary of current supernova detectors Baksan (1980-) 330 ton liquid scintillator ~100 e p  e + n events. No LVD (1992-) 1000 ton liquid scintillator. 840 counters 1.5m 3 each. 4 MeV thres., ~50% eff. for tagging decayed signal. ~300 e p  e + n events. No Super-K (1996-) 32,000 tons of water target. ~7300 e p  e + n, ~300 e  e scattering events. Yes KamLAND (2002-) 1000 ton liquid scintillator, single volume. ~300 e p, several 10 CC on 12 C, ~60 NC , ~300 p  p No ICECUBE (2005-) Gigaton ice target. By coherent increase of PMT single rates. High precision time structure measurement. No BOREXINO (2007-) 300 ton liquid scintillator, single volume. ~100 e p, ~10 CC on 12 C, ~20 NC , ~100 p  p No HALO (2010-) SNO 3 He neutron detectors with 76 ton lead target. ~40 events expected. No # of events expected for 10kpc.Directionality

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

Neutrino interaction in water ν ｅ + １６ O→e - + １ ６ F ν ｅ ＋ｐ → ｅ + +n ν ＋ e － →ν ＋ｅ － ν ｅ + １６ O→e + + １ ６ N COS  SN Cross section (H 2 O target) Angular distribution Neutrino Supernova

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

Identify e p events by neutron tagging with Gadolinium. Gadolinium has large neutron capture cross section and emit 8MeV gamma cascade. γ p n Gd e + 8 MeV ΔT~20μs Vertices within 50cm Future possible improvement in Super-K e 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 Captures on Gd Gd in Water % 0.001% 0.01% 0.1% 1% 100% 80% 60% 40% 20% 0% The main purpose of this project is to detect diffuse supernova neutrinos.

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

IceCube example Burst onset time Simulation of initial stage of a burst (10kpc supernova) Super-KamiokandeIceCube Halzen, Raffelt, arXiv: ~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.

IceCube (90˚S) cos  =  t / d If Super-K and IceCube has ~2 msec rise time resolution,  cos(  ) = ~0.1 (i.e. about 25 deg.). Beacom, Vogel, Phys.Rev.D60, , 1999 Triangulation on supernova direction Super-K (36˚N) d = 38 msec  Super-K resolution by electron-scattering is much better.

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

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

Cosmic Ultra High Energy neutrinos galactic Extra- galactic Ultra High Energy Cosmic Ray(UHECR) exists. “Horizon” of UHECR is ~50Mpc. cosmic rays interact with the microwave background (due to osc.) Neutrinos GZK neutrinos

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

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

GZK search IceCube Preliminary  e      All flavorlimits Systematic errors included Aya Ishihara (Chiba) From S.Yoshida

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.

Backups

Distance to Galactic supernova Mirizzi, Raffelt and Serpico, JCAP 0605,012(2006), astro-ph/ Core collapse type Type Ia 10kpc020kpc Based on birth location of neutron stars mean: 10.7 kpc r.m.s.: 4.9 kpc 7% probability < 3.16 kpc > x10 statistics 16% probability < 5 kpc > x 4 statistics 3% probability > 20 kpc < 1/4 statistics

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

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

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

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

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