The Baikal Experiment - Status, Results and Perspectives Zh. Dzhilkibaev for the Baikal Collaboration

1.Institute for Nuclear Research, Moscow, Russia. 2.Irkutsk State University, Irkutsk, Russia. 3.Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia. 4.DESY-Zeuthen, Zeuthen, Germany. 5.Joint Institute for Nuclear Research, Dubna, Russia. 6.Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia. 1. St.Petersburg State Marine University, St.Petersburg, Russia. 2. Kurchatov Institute, Moscow, Russia. The Baikal Collaboration

Nowadays operating neutrino telescopes: Baikal (NT-200) - Lake Baikal AMANDA II - South Pole Optical properties Deep underwater/underice particle detection Optical Module sensitivity (Baikal experiment) M.Markov: neutrino detection in natural transparent media (lakes, ocean, ice): - huge size (up to km 3 scale) detectors (AMANDA II ~ 1.5 Mton) - given optical parameters of medium, detection volume/area depends on cascades/muons energy (Baikal (NT-200) ~ ( ) Mton for ( ) Gev cascades energies) Cherenkov radiation intensity F (L) ~ I (E) exp(-L/L at ) I ~ 0.6 E /TeV, I ~ 10 8 E sh /TeV (60 m from

The Baikal Telescope NT-200 -NT-200 location and design -Selected results -NT-200+ status -Conclusion

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

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,… ) Winches used for deployment operations

Baikal Abs. Length: 22 ± 2 m Scatt. Length (geom) ~ m cos ~ Baikal - Optical Properties In-situ measurements FreshWater no K40 BG

9 The NT-200 Telescope -8 strings: 72m height 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=10 5 m 3

Few upward pointing pairs get hats against sedimentation Optical Module – Pair (Coincidence)

Atmospheric muon flux as a calibration source Time difference distributions t = t 52 -t 53 ) MC Experiment t, ns MC Experiment Ph.el. Amplitude distributions (ch.12)

Selected Results - Low energy phenomena atmospheric neutrinos neutrino signal from WIMP annihilation - Search for exotic particles magnetic monopoles - High energy phenomena neutrinos from GRB prompt muons and neutrinos diffuse neutrino flux

13 Atmospheric Muon-Neutrinos Thresh. ~ 15 GeV Skyplot (galactic coordinates) ~ 3° 3-dimensional reconstruction 84 events BG dominated bin

14 WIMP Neutrinos from the Center of the Earth + b + b W + + W - C + + Detection area of NT-200 for vertically up-going muons detection (after all cuts)

Neutrino induced muons E thr = 10 GeV Atmospheric neutrinos (Bartol-96 flux, oscillations - SK, K2K) WIMP Search

Applied cuts efficiency - experiment - atm. muons (expectation) - neutrinos (with oscillations) - neutrinos (without oscillations) WIMP Search

atm. neutrino flux - Bartol events - experiment 36.6 events - expected without oscillations 29.7 events - expected with oscillations Angular distributions (502 days, NT-200) atm. neutrino flux - Bartol-96 F Honda et al. - 04) = 0.7 F Bartol-96) no osc. osc.

Excess neutrino induced upward muon flux 90% c.l. limits from the Earth ( 502 days of NT-200 livetime, E > 10 GeV ) WIMP Search

Search for fast monopoles ( 780 livedays Monopole limit (90% C.L.) N = n 2 (g/e) 2 N = 8300 N g = 137/2, n = 1.33 Event selection criteria: hit channel multiplicity - N hi t > 35 ch, upward-going monopole - (z i -z)(t i -t)/( t z ) > 0.45 & o Background - atmospheric muons N hit distributions

Search for slow massive monopoles (10 -5 < -3 cat M+p M+e + (+ …), ~10 5 NT detection of massive bright objects (GUT-monopoles, nuclearites, Q-balls …) monopole trigger: N hit >4 within dt=500 sec selection requirements - N ch >1 with N hit >14 MACRO 150 days life time

21 Search for High Energy - Cascades NT-200 large effective volume Look for upward moving light fronts. Signal: isolated cascades from neutrino interactions Background: Bremsshowers from h.e. downward muons Final rejection of background by energy cut (N channel ) (BG)

High energy cascade selection: t min = min(t i - t j ), j > i - cascades below NT-200 N hit > 15 ch. - hit channel multiplicity Data (N hit >40 ch.) Data (t min >-10 нс)

Hit channel multiplicity (experiment) AE - hit channel multiplicity cut atm cut

Search for neutrinos correlated to Gamma Ray Bursts Data consistent with expected background from atm. muons 90% C.L. limits on neutrino flux from GRBs: N hit >34 1 selected event, N bg =0.47 F(E)=A tot E-E 0 ), A tot =N 90 /S(E 0 ) A GRB = A tot /N tot April February 2001: N tot = 722 BATSE events NT-200: N hit >10 & t min >-10 ns & t BATSE -100 ns < t < t BATSE +100 ns

Event selection criteria High energy cascades - experiment - atm. muons background

Prompt atmospheric muons and neutrinos ( source of background for neutrino telescopes ) Neutrinos - e : cascades (CC, NC) E -2.6, EE b = GeV Muons: cascades (e + e -, brem, ph.-nucl.) E -2.6 Predictions: ZHV - E.Zas, F.Halzen, R.Vazquez-93 RVS - O.Ryazhskaya, L.Volkova, O.Saavedra-02 QGSM, RQPM - E.Bugaev et al.-89 TIG - M.Thunman, G.Ingelman, P.Gondolo-96 GGV - G.Gelmini, P.Gondolo, G.Varieschi-02 (hep-ph/ ) Sources - decays of short-lived particles ( D, …) isotropic for E < 10 7 GeV 90% c.l. limits for prompt and e fluxes (780 life days)

The 90% C.L. Limits Obtained With NT-200 (780 days) DIFFUSE NEUTRINO FLUX (Ф ~ E -2, 10 TeV < E < 10 4 TeV) e = (AGN) e = (Earth) Diffuse flux of e,, : cascades W-RESONANCE ( E = 6.3 PeV, 5.3 · cm 2 ) Ф e < 4.2 · (cm 2 · s · sr · GeV ) -1 Ф e < 5.0 · (cm 2 · s · sr · GeV ) -1 (AMANDA04) E 2 Ф < 1.0 ·10 -6 GeV cm -2 s -1 sr -1 E 2 Ф < 8.6 ·10 -7 GeV cm -2 s -1 sr -1 (AMANDA04) V g (NT-200) AMANDA II

Diffuse flux of e,, : cascades Experimental limits and theoretical predictions SS SP SDSS D.Semikoz, G.Sigl 04 Models ruled out by AMANDA04 SDSS - Stecker et al.92 SS - Stecker, Salamon96 SP - Szabo, Protheroe92 MPR MPR - Mannheim, Protheroe, Rachen

Upgrade to NT : two distant test string 2005: completion 36 additional PMTs on 3 far strings 4 times better sensitivity ! PeV Mton

Cascade coordinates (energy) reconstruction efficiency NT

NT-200+ status 2004: - new cable to shore - DAQ system has been improved - two of three outer strings are installed common events are taken during 364 hours life time (0.017 Hz)

NT as subunit for a Gton scale detector NT

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

CONCLUSION - successfully running since 10 years - strong in HE-diffuse search (shower) and exotic particles (monopoles): Mton detector - good GRB-sensitivity, complementary to AMANDA - relevant other results: WIMP - upgrade to NT-200+ in R&D Gigaton Volume Detector (km3)

year anniversary celebration

Экспериментальный материал Гамма-всплески (эксперимент BATSE) Декабрь предварительные результаты Основные параметры GRB - время регистрации - длительность - направление на вспышку - энергия вспышки Темп регистрации ~ 1 событие/день Основной каталог BATSE (triggered GRB) Каталог Штерна (non-triggered GRB) ~ 80% Данные с 1991 по 2000 год BATSE GRB Final Sky Map T_90

Экспериментальный материал Cобытия NT-200 Декабрь предварительные результаты Основные параметры событий Т - время регистрации М - множественность триггированных ОМ (характеризует энергию ливня) t - разность времен срабатываний ОМ (характеризует направление прихода) Критерии отбора событий M > 10 OM t < 10 ns Эффективно отбираются горизонтальные ливни и ливни из нижней полусферы Темп регистрации - ~10 -2 с Данные апрель февраль 2000

Поиск временных корреляций Декабрь предварительные результаты Статистика экспериментальных данных В анализируемый период апрель февраль 2000 c периодом чувствительности NT-200 совпало 386 GRB по основному каталогу BATSE и 336 по каталогу Штерна (>1 часа непрерывной экспозиции в области GRB). Количество GRB из основного каталога BATSE (B) и каталога Штерна (S) Up, Down – GRB из верхней и нижней полусферы

Поиск временных корреляций Декабрь предварительные результаты Поиск коррелированных во времени событий в области GRB Оценивалось количество событий в интервалах dt = 1, 2,... 5 секунд в области GRB (поиск кластеров событий с множественностью К)

Поиск временных корреляций Декабрь предварительные результаты Анализ корреляций для различных порогов регистрации Оценивалось суммарное количество событий для всех GRB при различных множественностях М

Предел на поток нейтриино Декабрь предварительные результаты Sef N 90 - верхний 90% предел на количество событий S - эффективная площадь - нормированный поток нейтрино