Physics results and perspectives of the Baikal neutrino project B. Shoibonov (JINR, Dubna) for the Baikal collaboration February 2009

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The Baikal Experiment - Status, Results and Perspectives

The Site3.6 km to shore1.1 km depth Absorption Length: ~25 mScatt. Length (geom) ~ 30-60 m ~ 0.85-0.9

3600 m1366 mNT200+ 4-string stage (1996)One of the first neutrinoevents recorded with thefour-string version NT96 1990 - Proposal NT2001993 NT36 (36 PMTs at 3 strings) The First Underwater Neutrino Array ever built 3-dimensional Muon reconstruction Verify BG-suppression & check MC/Water/.. First underwater neutrino eventsBaikal - Milestones1998 NT200 (192 PMTs at 8 strings) Full Physics program startedsince 2005 - Activity towards Gigaton Volume Detector in Lake Baikal2005 NT200+ (NT200 + 3 long external strings)2008 New technology prototype stringOutline:

1. Physics Results (selected) : NT200 1998-2002 Search for point sources Search for a diffuse flux of HE neutrinos Search for fast magnetic monopoles Search for neutrinos from WIMP annihilation Search for GRB correlated neutrino flux *(Acoustic neutrino detection activity)2. Gigaton Volume Detector in Lake Baikala) NT200+ (10 Mt Detector) - intermediate stage to GVDb) New technology prototype string


Ice as a natural deployment platformThick ice stable for 6-8 weeks/year: Maintenance & upgrades Test & installation of new equipmentWinches are used for deployment

Winches used for deployment Winches used for deploymentNT200+=NT200 + 3 long externalstrings- Height = 210m = 200m Volume ~ 5 Mton

New technology stringThe NT-200 Telescope

-8 strings: 72m height - 192 optical modules = 96 pairs (coincidence)- measure T, Charge - T ~ 1 ns - dyn. range ~ 1000 p.e.Effective area: 1 TeV ~2000 m Eff. cascade volume: 0.2Mt (10TeV) Quasar PM: =37cmHeight x = 70m x 40m, Vinst=105 m3

Search for point sources 372 events (1998-2002, 1008 live days) MC: 385 ev. Expected (20%BG). Angular resolution is 2.2 degrees Ethr ~ 15-20 GeV- No indication for Point Sources found.

AMANDA:2000-2003, Baikal: 1998-2002galactic coordinates

Galactic coordinatesExposure map10

SKMACROBaksan Using Baksan estimationsfor MSSM(P=0.5; ma =52.5GeV; tgb=8))

+ b + b W + + W -C + + WIMP Neutrinos from the Center of the EarthFrom the Earth centerSearch for high energy neutrinosEvents with upward moving light signals are selected (BG)

NT200ne cascadesNT200large effective volumeAllowed by excellent scatt scatt=30-50m Radius, m New analysis based on reconstruction of cascade coordinates, direction and energy increases efficiency of selecting neutrino events. Selecting HE Cascades

Cuts: tmin > -10 ns, Nhit > 18, 2 < 3, LA < 20

No events observed ( 24% system. err.) n90% = 2.4 The 90% C.L. all flavour limit (1038 days) for a =2 spectrum ~ E-2 (20 TeV < E < 20 PeV), and assuming e:: = 1 1 1 at Earth (1 2 0 at source) E2 n < 2.9 10-7 GeV cm-2 s-1 sr-1 (Baikal 2008) Final Cut: Esh > 130 TeVCascade energy distribution Volume for cascades E 100 TeV: Veff~ 0.5-1 km dlg(E) ~ 0.1, dmed < 4o

Muon threshold ~10-30 TeV Eff. area for muons Seff ~ 0.2-0.3 km2 A future Gigaton (km3) Detector in Lake Baikal. Sparse instrumentation: ~2000 OMs12 clusters X 8 strings~400 m string height~20 OMs per stringInterstring distances ~100m*(MC optimization is in progress)


NT200+ - intermediate stage to Gigaton Volume Detector (km3 scale) has been operating since 2005Main R&D goal: verify many new key elements and design principles of the future km3-scale telescopeMain Physics goal: energy spectrum of all flavor extraterrestrial HE-neutrinos (E > 100 TeV)Total number of OMs 228 / 11 stringsInstrumented volume 5 MtDetection volume >10 Mt for En>10 PeV

High resolution of cascade vertex and energy neutrino energy

Light sourceIce camp view during winter expeditionInstallation of a new technology string as an integral part of NT200+ (April 2008)

Investigation and in-situ tests of basic knots of future detector: optical modules, DAQ system, new cable communications.

Studies of basic DAQ/Triggering approach for the km3-scale detector.

Confrontation of classical TDC/ADC approach with FADC readout.

New technology prototype string for a km3 Baikal neutrino telescope

13 Hamamatsu R8055 12 Photonis XP 1807Summary

For the planned km3-detector in lake Baikal, R&D-activities have been started.

The existing NT200+ allows to verify all key elements and design principles of km3-detector.

A full scale new technology string was installed in spring 2008 as an integral part of NT200+ for investigation and in-situ tests of basic knots of future detector: optical modules, DAQ system, new cable communications.