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A search for high energy neutrinos with Baikal neutrino telescope NT-200

A search for high energy neutrinos with Baikal neutrino telescope NT-200. Zh. Dzhilkibaev for the Baikal Collaboration. The Baikal Collaboration. Institute for Nuclear Research, Moscow, Russia. Irkutsk State University, Irkutsk, Russia.

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A search for high energy neutrinos with Baikal neutrino telescope NT-200

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  1. A search for high energyneutrinos with Baikal neutrino telescope NT-200 Zh. Dzhilkibaev for the Baikal Collaboration

  2. The Baikal Collaboration Institute for Nuclear Research, Moscow, Russia. Irkutsk State University, Irkutsk, Russia. Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia. DESY-Zeuthen, Zeuthen, Germany. Joint Institute for Nuclear Research, Dubna, Russia. Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia. St.Petersburg State Marine University, St.Petersburg, Russia. Kurchatov Institute, Moscow, Russia.

  3. Energy spectrum of neutrinos emitted by different celestial bodies. Underground telescopes Underwater/ice telescopes EAS-arrays/radio/acoustic MeV – TeV 10 GeV – EeV >EeV Baksan Baikal (NT-200) AGASA, HiRes, Auger, TA MACRO AMANDA EUSO, RICE, ANITA, FORTE SuperKamiokande V ~ 104 – 106 (?) m3 V ~ 106 – 109 m3 S ~ 103 km2

  4. Deep underwater/underice particle detection 1960 - M. Markov: neutrino detection in natural transparent media (lakes, ocean, ice): • - huge size (up to km3 scale) detectors • (AMANDAII ~ 1.5 Mton) • - given optical parameters of medium, • detection volume/area depends on • cascades/muons energies (Baikal NT-200 ~ 0.1 - 6 Mton for 104 - 107 Gev cascades energies) Cherenkov radiation intensity F(L)~ I (E) exp(-L/Lat) I ~ 0.6 E/TeV, I ~ 108 Esh/TeV Nowadays operating neutrino telescopes: Baikal (NT-200) - Lake Baikal AMANDA II - South Pole Optical properties Optical Module sensitivity (Baikal experiment)

  5. 3600 m 1366 m NT-200 The Site • 4 cables x 4km to shore. • 1070m depth

  6. Winches used for deployment operations  Ice as a natural deployment platform • Ice stable for 6-8 weeks/year: • Maintenance & upgrades • Test & installation of new equipment • Operation of surface detectors (EAS, acoustics,… )

  7. FreshWater  no K40 BG Baikal Baikal Abs. Length: 22 ± 2 m Scatt. Length (geom) ~ 30-50 m cos ~ 0.85-0.9 Baikal - Optical Properties In-situ measurements

  8. -8 strings: 72m height - 192 optical modules • pairwise coincidence  96 space points • calibration with N-lasers • timing ~ 1 nsec • Dyn. Range ~ 1000 pe Effective area: 1 TeV ~2000 m² Eff. shower volume: 10TeV ~0.2Mt Quasar PMT: d = 37cm Height x  = 70m x 40m, V=105m3 The NT-200 Telescope 9

  9. Few upward pointing pairs get „hats“ against sedimentation Optical Module – Pair (Coincidence)

  10. Atmospheric muon flux as a calibration source Time difference distributionst = t52-t53) MC Experiment Amplitude distributions (ch.12) MC Experiment t, ns Ph.el.

  11. Selected Results • Low energy phenomena atmospheric neutrinos neutrino signal from WIMPs annigilation • Search for exotic particles magnetic monopoles • High energy phenomena neutrinos from GRB prompt muons and neutrinos diffuse neutrino flux

  12.  AE- hit channel multiplicity NT-200  large effective volume Search for High Energy -Cascades 1.5 2 (BG) 2.5 atm.m 14

  13. Calibration light source (water laser) Laser location - 20 m below NT-200 Channel 49 - L49 = 90 m, Channel 50 – L50 = 85 m Channel 51 – L51 = 78 m Amplitudes , ph. e l. Time differences, ns Light intensity Reconstruction of laser coordinates Reconstruction of laser intensity

  14. Cascades below NT-200 Calibration light source tmin = min(ti – tj) > -10 нс, i<j Atmospheric muons N hit > 40 Hit channel multiplicity tmin > -100 нс, Nhit > 40

  15. Data analysis April 1998 – February 2003 NT-200 effective configurations 1038 live-days 3.45x108 (muon trigger >3 hit channels) 22597 events – (Nhit >15, tmin > -10 ns) Experimental data consistent with background expectation The tmin distributions Hit channel multiplicity

  16. Selection criteria • - experiment • - atm. muons background Events distribution in (Nhit , tmin )-space High energy cascades (MC)

  17. Dependence of detection efficiency on a shape of neutrino flux Fn~ E-g Detection probability Detection energy range (90% of expected events)

  18. Zenith angular distribution of expected events (isotropic initial neutrino flux) Zenith angle ranges which contain 90% of expected events Detection probability vs. zenith angle for five decades in neutrino energy range 104 – 109 GeV

  19. Detection volumes Neutrino induced cascades Coordinates of cascade origin AMANDA II Vg(NT-200)

  20. Upper limits on diffuse neutrino fluxes No evidence for neutrino-induced cascades above the background Fn = Afin(E) – initial flux; ne : nm : nt = 1 : 2 : 0 - AGN fin(E) – any assumed ne : nm : nt = 1 : 1 : 1 - Earth The number of expected events during observation time T Nmodel = Amodel T тdW тdEsh Vefт S(En ЮEsh) f(En) dEn 90% C.L. an upper limit on the number of signal events (with an error on the signal detection efficiency 24%) n90=2.5 n90/Nmodel – model rejection factor

  21. Model rejection factors for models of astrophysical neutrino sources Upper limit on ~E-2diffuse neutrinoflux E2F< 8.1 ·10-7GeV cm-2 s-1 sr-1 (Baikal) E2 Ф< 8.6 ·10-7GeV cm-2 s-1 sr-1 (AMANDA II) W-RESONANCE ( E = 6.3 PeV, 5.3 ·10-31 cm2 ) Baikal Фe < 3.3 · 10-20 (cm2 · s · sr ·GeV )-1 AMANDA II Фe < 5.0 · 10-20 (cm2 · s · sr ·GeV )-1 Model rejection factor n90 /Nmodel

  22. Bounds for models of extragalactic neutrino production and experimental upper limits on ~E-2 diffuse neutrino flux Experimental upper limits on fluxes produced in central region of AGN (SS) and in AGN jets (SeSi)

  23. 2005: has been put in operation! 110100 1000PeV 41523 40Mton 36 additional PMTs on 3 far ‘strings‘  4 times better sensitivity ! Upgrade to NT-200+

  24. NT - 200+ Cascade coordinates (energy) reconstruction efficiency

  25. NT - 200+ NT - 200+ as subunit for a Gton scale detector

  26. A Gigaton (km3) Detector in Lake Baikal. Sparse instrumentation: 91 strings with 12 OM = 1308 OMs  effective volume for 100 TeV cascades ~ 0.5 -1.0 km³!  muon threshold between 10 and 100 TeV

  27. CONCLUSION • Experimental limits on diffuse extragalactic neutrino fluxes • where derived from data collected during 1038 live days by • NT-200 neutrino telescope. In the energy range 20 Tev – 50 Pev • these limits are currently the most restrictive or close to limits • obtained by AMANDA experiment • In 2005 neutrino telescope NT-200+ was put in operation. • With an effective volume about 10 – 20 Mton this array • will allow to test most of theoretically predicted fluxes • of extragalactic neutrinos

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