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

2. 1.Institute for Nuclear Research RAS, Moscow, Russia. 2.Irkutsk State University, Irkutsk, Russia. 3.Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia. 4.Joint Institute for Nuclear Research, Dubna, Russia. 5.DESY-Zeuthen, Zeuthen, Germany. 6.Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia. 7. St.Petersburg State Marine University, St.Petersburg, Russia. 8. Kurchatov Institute, Moscow, Russia. The Baikal Collaboration ~50 authors

3. The underwater detection was suggested by M.Markov and K.Greisen in 1960. It is based on registration of cherenkov radiation of induced charged particles Physics Background: atmospheric neutrinos A. Point sources “Find the sources on the sky” + high angular resolution - needs strong enough single sources B. Anomalies in atmospheric spectrum + high energy resolution + all weak point sources should add up + model predictions ~ experimental sensitivities Astrophysical ’s: two detection methods Skyplot with Hot spot(s) (galactic coordinates) Muons from (CC)  N  µ X Electron / hadron cascades from CC + NC e /  / (  ) log [ E 2 · Flux(E ) 3 96 AGN atmospheric log (E /GeV)

4. The Site ● 3.6 km to shore ● 1.1 km depth ● Absorption Length: ~25 m ● Scatt. Length (geom) ~ 30-60 m ~ 0.85-0.9 3600 m 1366 m NT200+

5. Ice as a natural deployment platform Thick ice stable for 6-8 weeks/year: – Maintenance & upgrades – Test & installation of new equipment Winches are used for deployment

6. 4-string stage (1996) One of the first neutrino events recorded with the four-string version NT96 ● 1990 - Proposal NT200 NT36 ● 1993 – 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 events Baikal - Milestones NT2001998 – NT200 (192 PMTs at 8 strings) F ull Physics program started since 2005 - Activity towards Gigaton Volume Detector in Lake Baikal 2005 – NT200+ (NT200 + 3 long external strings) 2008 – „New technology“ prototype string

7. NT200+ = NT200 + 3 long external strings - Height = 210m - = 200m -  = 200m - Volume ~ 5 Mton “New technology” string

8. Outline: 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 Baikal - a) NT200+ (10 Mt Detector) - intermediate stage to GVD - b) “New technology” prototype string - Conclusion

9. The NT-200 Telescope -8 strings: 72m height - 192 optical modules = 96 pairs (coincidence) - measure T, Charge - σ T ~ 1 ns - dyn. range ~ 1000 p.e. Effective area: 1 TeV ~2000 m² Eff. cascade volume: 0.2Mt (10TeV) Quasar PM:  =37cm Height x  = 70m x 40m, V inst =10 5 m 3

10. Search for point sources - 372 events (1998-2002, 1008 live days) - MC: 385 ev. Expected (20%BG). - Angular resolution is 2.2 degrees - E thr ~ 15-20 GeV - No indication for Point Sources found. AMANDA:2000-2003, Baikal: 1998-2002 galactic coordinates Galactic coordinates Exposure map

11. SK MACRO Baksan Using Baksan estimations for MSSM(P=0.5; m a =52.5GeV; tg  =8))  +   b + b  W + + W - C +  +  WIMP Neutrinos from the Center of the Earth From the Earth center

12. Search for high energy neutrinos Events with upward moving light signals are selected  („BG“) e cascades NT200 large effective volume Allowed by excellent scatt  scatt =30-50m Radius, m

13. New analysis based on reconstruction of cascade coordinates, direction and energy increases efficiency of selecting neutrino events. Selecting HE Cascades Cuts: t min > -10 ns, N hit > 18, χ 2 < 3, L A < 20 No events observed ( 24% system. err.)  n 90% = 2.4 The 90% C.L. “all flavour” limit (1038 days) for a  =2 spectrum Ф ~ E -2 (20 TeV < E < 20 PeV), and assuming e :  :  = 1  1  1 at Earth (1  2  0 at source) E 2 Ф < 2.9 ·10 -7 GeV cm -2 s -1 sr -1 (Baikal 2008) Final Cut: E sh > 130 TeV Cascade energy distribution

14.  Volume for cascades E ≥ 100 TeV: V eff ~ 0.5-1 km³ dlg(E) ~ 0.1, d ψ med < 4 o  Muon threshold ~10-30 TeV  Eff. area for muons S eff ~ 0.2-0.3 km 2 A future Gigaton (km3) Detector in Lake Baikal. Sparse instrumentation: ~2000 OMs 12 clusters X 8 strings ~400 m string height ~20 OMs per string Interstring distances ~100m * (MC optimization is in progress)

15. NT200+ - intermediate stage to Gigaton Volume Detector (km3 scale) has been operating since 2005 Main R&D goal: verify many new key elements and design principles of the future km3-scale telescope Main Physics goal: energy spectrum of all flavor extraterrestrial HE-neutrinos (E > 100 TeV) Total number of OMs – 228 / 11 strings Instrumented volume – 5 Mt Detection volume >10 Mt for E n >10 PeV High resolution of cascade vertex and energy neutrino energy Light source

16. Ice camp view during winter expedition

17. Installation 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 1807

18. Summary 1.For the planned km3-detector in lake Baikal, R&D- activities have been started. 2.The existing NT200+ allows to verify all key elements and design principles of km3-detector. 3.A full scale “new technology” string was installed in spring 2008 as an integral part of NT200+ for i 3.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.