Physics results and perspectives of the Baikal neutrino project

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

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

3. atmospheric log [ E2 · Flux(E) AGN 3 6 9 Astrophysical ’s: two detection methods 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 Skyplot with Hot spot(s) (galactic coordinates) Muons from (CC)  Nµ X Electron / hadron cascades from CC + NC e/ / () log (E /GeV)

4. The Site 3600 m • 3.6 km to shore • 1.1 km depth • Absorption Length: ~25 m • Scatt. Length (geom) ~ 30-60 m <cos θ> ~ 0.85-0.9 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. One of the first neutrino events recorded with the four-string version NT96 • 1998 – NT200 (192 PMTs at 8 strings) • Full 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 4-string stage (1996) Baikal - Milestones • 1990 - Proposal NT200 • 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

7. 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

8. -8 strings: 72m height - 192 optical modules = 96 pairs (coincidence) - measure T, Charge - σT ~ 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, Vinst=105 m3 The NT-200 Telescope

9. Search for point sources Exposure map AMANDA:2000-2003, Baikal: 1998-2002 galactic coordinates Galactic coordinates • 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.

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

11. Selecting HE Cascades New analysis based on reconstruction of cascade coordinates, direction and energy increases efficiency of selecting neutrino events. Cuts: tmin> -10 ns, Nhit > 18, χ2 < 3, LA < 20 Final Cut: Esh > 130 TeV Cascade energy distribution No events observed ( 24% system. err.) n90% = 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) E2 Фn< 2.9 ·10-7GeV cm-2 s-1 sr-1 (Baikal 2008)

12. A future Gigaton (km3) Detector in Lake Baikal. Sparseinstrumentation: ~2000 OMs 12 clustersX 8 strings ~400 m stringheight ~20 OMs per string Interstring distances ~100m  Volume forcascades E ≥ 100 TeV: Veff~ 0.5-1 km³ dlg(E) ~ 0.1, dψmed< 4o  Muon threshold ~10-30 TeV  Eff. area for muons Seff ~ 0.2-0.3 km2 *(MC optimization is in progress)

13. 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) Light source Total number of OMs – 228 / 11 strings Instrumented volume – 5 Mt Detection volume >10 Mt for En>10 PeV High resolution of cascade vertex and energy neutrino energy

14. Ice camp view during winter expedition

15. “New technology” prototype string for a km3 Baikal neutrino telescope • 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. 13” Hamamatsu R8055 12” Photonis XP 1807

16. Summary • 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.