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Neutrino observatories

Gravitational-wave Physics&Astronomy Workshop, January 28, 2011 . M.Nakahata. Neutrino observatories. Kamioka observatory ICRR/IPMU, Univ. of Tokyo. SN1987A. Contents. Supernova burst neutrinos How they are produced SN1987A Current detectors in the world

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Neutrino observatories

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  1. Gravitational-wave Physics&Astronomy Workshop, January 28, 2011 M.Nakahata Neutrino observatories 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. Neutron star Core-collapse supernova Standard scenario of the core-collapse supernova Core-collapse Neutrino trapping Core bounce C+O He Si n n H Fe n n n n n Supernova burst Shock wave propagation Shock wave at core n n n n n Figure from K.Sato

  4. Neutrino emission from supernova burst Released gravitational energy: ~3x1053erg Neutrinos carry almost all (99%) of the energy. Energy for explosion and optical emission is only ~1%(~1051erg). Expected time profile (x=m,t) Livermore simulation Mean neutrino energy (x=m,t) T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998)

  5. SN1987A: supernova at LMC(50kpc) 95 % CL Contours 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 Total Binding Energy Theory _ Spectral neTemperature from G.Raffelt

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

  7. The Baksan underground scintillation telescope (Russia) Total number of standard detectors…………..3150 Total target mass…………………….…...330 tons of oil-based scintillator E.N.Alexeyev, L.N.Alexeyeva, astro-ph/0212499 • ~100 nepe+nevents 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 m3 each. Total target: 1000 t liquid scintillator 4MeV threshold With<1MeVthreshold for delayed signal (neutron tagging efficiency of 50 +- 10 %) E resolution: 13%(1s) at 15MeV • ~300 nepe+nevents expected for 10 kpc SN. At Gran Sasso Lab., Italy From W.Flugione

  9. Single volume liquid scintillator detectors KamLAND Borexino SNO+ (Kamioka, Japan) (Gran Sasso, Italy) (SNO Lab.,Canada) • 300ton liq.sci. • Running since 2007. 1000ton liq.sci. 1000ton liq.sci. Running since 2002. Under construction. From K.Inoue, G.Bellini, M.Chen

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

  11. CC: NC: HALO - a Helium and Lead Observatory (SNO Lab., Canada) SNO 3He neutron detectors with lead target HALO-1is using an available 76 tonnes of Pb • In HALO-1 for a SN @ 10kpc†, • Assuming FD distribution with T=8 MeV for μ’s, τ’s. • 65 neutrons through e charged current channels • 20 neutrons through νx 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 (South pole) IceTop Design Specifications • Fully digital detector concept • Number of strings – 75 • Number of surface tanks – 160 • Number of Optical modules (DOMs) – 4820 • Instrumented volume – 1 km3 1450m InIce AMANDA Supernova neutrinos coherently increase single rates of PMTs. 2450m Construction finished on Dec.18, 2010. From L.Koepke, S.Yoshida

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

  14. Super-Kamiokande detector (Kamioka, Japan) • 50,000 ton water • 32,000 ton photo-sensitive volume • ~2m OD viewed by 1885 8-inch PMTs • 32kt ID viewed by 11,100 20-inch PMTs • 22.5kt fid. vol. (2m from wall) • ~4.5MeV energy threshold • SK-I: April 1996~ • SK-IV is running LINAC Electronics hut Water and air purification system Control room Atotsu entrance ID 41.4m OD 1km (2700mwe) Ikeno-yama Kamioka-cho, Gifu Japan 3km 2km SK Mozumi Atotsu 39.3m

  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 ne+p events ~300 n+eevents ~360 16O NC g events ~100 16O CC events (with 5MeV thr.) for 10 kpcsupernova

  16. Summary of current supernova n detectors # of events expected for 10kpc. Directionality

  17. Super-Kamiokande: Water Cherenkov detector Cherenkov lightEmitted when particle travels faster than speed of light in water(c/1.33）. e q Emission angle = cos-1(1/nb)=42° • 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 νｅ＋ｐ→ｅ++n νｅ+１６O→e++１６N Cross section (H2O target) Angular distribution ν＋e－→ν＋ｅ－ Supernova n νｅ+１６O→e-+１６F COSqSN Neutrino

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

  20. Future possible improvement in Super-K 100% 80% 60% 40% 20% 0% Captures on Gd 0.1% Gd gives>90% efficiencyfor n capture In Super-K this means ~100 tons of water solubleGdCl3 or Gd2(SO4)3 • Identify nep events by neutron tagging with Gadolinium. • Gadolinium has large neutron capture cross section and emit 8MeV gamma cascade. ne n p Gd + e γ 8 MeV ΔT~20μs Vertices within 50cm The main purpose of this project is to detect diffuse supernova neutrinos. 0.0001% 0.001% 0.01% 0.1% 1% Gd in Water

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

  22. Burst onset time Simulation of initial stage of a burst (10kpc supernova) Super-Kamiokande IceCube Halzen, Raffelt, arXiv:0908.2317 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, 033007, 1999 Super-K (36˚N) cos = t / d d = 38 msec q IceCube (90˚S) If Super-K and IceCube has ~2 msec rise time resolution, cos() = ~0.1 (i.e. about 25 deg.). Super-K resolution by electron-scattering is much better.

  24. SuperNova Early Warning System snews.bnl.gov arXiv:0803.0531 Details: arXiv:astro-ph/0406214 Individual supernova-sensitive experiments send burst datagrams to SNEWS coincidence computer at Brookhaven National Lab(backup at U. of Bologna) Email alert to astronomers if coincidence in 10 seconds Participating experiments: Large Volume Detector (Italy) Super- Kamiokande (Japan) IceCube (South Pole) SNO (Canada) until end of 2006 From K. Scholberg

  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. e e+  Possible sources: AGN, supernova remnants, …. + + sync p sync e- Black hole accretion disk

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

  27. Detectors for High Energy Astrophysical Neutrinos Antares • Mediterranean sea • 0.2x0.2x0.4km • Volume: 0.01 km3 • Running since May 2008 • South pole • Volume:1 km3 • Construction finished in Dec.2010 NT200+ • Lake Bikal • 0.2 kmf 0.2 kmh • Volume: 0.01 km3 • Running from 2006

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

  29. GZK n search All flavor (ne + nm + nt) 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/0604300 Based on birth location of neutron stars Core collapse type mean: 10.7 kpc r.m.s.: 4.9 kpc Type Ia 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 ne+p ne+p ne+p Without nepidentification by neutron tagging n+e n+e n+e n+e SN at 10kpc

  34. Accuracy of supernova direction with neutron tag Thomas, Sekikoz, Raffelt, Kachelriess, Dighe, hep-ph/0307050v2 Accuracy of SN direction with 40000 simulated supernova Tagging efficiency vs. accuracy (95% CL) G: Garching model, L: Livermore model a: normal hierarchy sin2q13>10-3 b: inv. hierarchy sin2q13>10-3 c: any hierarchy sin2q13<10-3 Accuracy can be improved by a factor of two with neutron tagging.

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

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

  37. n+p elastic signal（ n+p→ n+p） at liq. Scintillator detectors nmnmntnt Solid: sum of all ne ne Beacom, Farr, and Vogel, PRD66, 033001(2002) Sensitivity of temperature measurement Expected spectrum Determine original nm, nm, nt, nttemperature with ~10% accuracy. (free from neutrino oscillation.） ~300 events/ktabove 200keV ~150 events/ktabove 500keV Current Borexino threshold: 200keV Current KamLAND threshold: 600~700keV(will be lowered after 2008 distillation.)

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