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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 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 Neutrinos carry almost all (99%) of the released gravitational energy (~3x1053 erg.) Kinetic and optical energies are only ~1%(~1051erg). Expected time profile Livermore simulation Mean neutrino energy 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-K 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. Criteria of serious candidate: ≥ 9 events/20sec in inner 130ton detectors. (sensitive up to ~20kpc) From E.N.Alexeyev

  8. LVD detector LVD consists of an array of 840 counters, 1.5 m3 each. Total target: 1000 t of CnH2n 900 t of Fe 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 liq. 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 g from 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 Spectrum measurement of higher energy component. Independent from neutrino oscillation. 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-1 is 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 DOMs – 4820 • Instrumented volume – 1 km3 • Angular resolution < 1.0° InIce AMANDA 19 Strings 677 Modules Construction finished on Dec.18, 2010. Supernova neutrinos coherently increase signal rates of PMTs. 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+e events ~360 16O NC g events ~100 16O CC events (with 5MeV thr.) for 10 kpc supernova

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

  17. 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

  18. 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° One of the SN1987A events in Kamiokande

  19. Neutrino interaction in water νｅ＋ｐ→ｅ++n νｅ+１６O→e++１６N Angular distribution Cross section Supernova n ν＋e－→ν＋ｅ－ νｅ+１６O→e-+１６F COSqSN Neutrino

  20. Angular distribution of νｅ＋ｐ→ｅ++n νｅ＋ｐ→ｅ+＋ n neutrino energy P.Vogeland J.F.Beacom, Phys.Rev.D60(1999)053002. COSqSN

  21. 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

  22. 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 diffused supernova neutrinos. 0.0001% 0.001% 0.01% 0.1% 1% Gd in Water

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

  24. Super-K: Angular distribution (with Gd) ne+p ne+p ne+p ne+p With nep identification by neutron tagging n+e n+e n+e n+e SN at 10kpc

  25. 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.

  26. Precision of 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.

  27. 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.

  28. 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

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

  30. 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.)

  31. Detectors for Cosmic High Energy 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

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

  33. GZK n search All flavor (ne + nm + nt) limits Systematic errors included IceCube Preliminary Aya Ishihara (Chiba) From S.Yoshida

  34. Conclusions • Supernova burst neutrinos • Many detectors in the world with various types of signals. • ~8,000 events expected at Super-K. • 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.

  35. Backups

  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. Super-K: Time variation measurement by ne+p Assuming a supernova at 10kpc. nep e+nevents give direct energy information (Ee = En – 1.3MeV). Time variation of event rate Time variation of mean energy Enough statistics to discuss model predictions

  38. 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, nt temperature with ~10% accuracy. (free from neutrino oscillation.） ~300 events/kt above 200keV ~150 events/kt above 500keV Current Borexino threshold: 200keV Current KamLAND threshold: 600~700keV(will be lowered after 2008 distillation.)

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