1. The BAIKAL Neutrino Telescope: Results and Plans 19 th ERCS, Florence, Italy,September 3 rd, 2004 Ralf Wischnewski DESY-Zeuthen

2. R.Wischnewski ECRS2004 2 HE Neutrino Detection: Muons and “Cascades” O(km) long muon tracks direction determination by Cherenkov light timing  5-15 m - Good directionality by Cherenkov timing - Poor energy resolution Charged Current (CC)  Electromagnetic & hadronic cascades ~ 5 m - Good energy resolution - Bad pointing CC e  + Neutral Current

3. The case for “All flavor” detection (1) - Oscillation transfers the canonical e :  :  = 1: 2: 0 at source (e.g. from  +- decay) to e :  :  = 1: 1: 1 at earth  50 % of signal  are ‘lost’ !  Catch all flavours (2) Earth is opaque for ‘upward’ at E >> PeV. But:  regenerate via  -decay and pile up at transparency E-threshold, i.e. do not ‘disappear’.

4. The case for >1 Uw/Ice - Telescopes (1) Complete sky coverage Lake Baikal South Pole Sky coverage in Gal.Coordinates = galactic center South Pole (AMANDA) Lake Baikal (and Mediterranean...) Visibility: below local horizon - white = 100% visibility - black = „blind region“

5. The case for >1 Uw/Ice - Telescopes (1) Complete sky coverage Lake Baikal South Pole (2) Complementarity of detectors –Optical medium: scattering vs. no-scatt. –Effective volume: contained vs. external –Pattern recognition & filtering criteria

6. R.Wischnewski ECRS2004 6 -NT-200 design + history -Results: - Atm. Neutrinos, WIMPs, Monoples, - Cascades  AP neutrinos, muons -Physics upgrade to NT-200+ to be finished in April 2005 Outline

7. R.Wischnewski ECRS2004 7 Collaboration Russia – Germany - Institute of Nuclear Research, Moscow - Moscow State University - DESY Zeuthen - Irkutsk State University - Nishni Novgorod State Technical University - State Marine Technical University, St.Petersburg - Kurchatov Institute, Moscow - JINR, Dubna ~45 authors

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

9. 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 

10. R.Wischnewski ECRS2004 10 The Ice Camp (4km offshore)

11. R.Wischnewski ECRS2004 11 The NT-200 Telescope -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 geo =10 5 m 3 = 0.1Mton

12. R.Wischnewski ECRS2004 12 Optical Module – Pair (Coincidence)

13. R.Wischnewski ECRS2004 13 21.5 m long arms allow for separate String manipulation 8 Strings on a Heptagon frame d=40m N.B.: Flexiblity - additional (external) strings can be deployed independently (and re-positioned) at any place.

14. R.Wischnewski ECRS2004 14 NT-36, April 1993...and retrieval one year later. Final deployment of the Heptagon …

15. Abs. Length: 22 ± 2 m Scatt. Length (geom) ~ 30-50 m  cos  ~ 0.85-0.9 In-situ measurements over many years 2001: Cross calibration with NEMO/ANTARES L att -device Baikal, nm Absorption cross section, m -1 Scattering cross section, m -1 FreshWater  no K40 BG Optical Properties

16. R.Wischnewski ECRS2004 16 Baikal - History Since 1980 – Site tests and early R&D started 1989/90 - Proposal NT-200, start construction NT-361993 – NT-36 started 13.4.93 (36 PMTs at 3 strings)  The First Underwater Array ever built  3-dimensional Muon reconstruction  Verify BG-suppression & check MC/Water/..  First 2 Neutrino Candidates NT-200 commissioned 06.04.981998 – NT-200 commissioned 06.04.98 (192 PMTs at 8 strings)  Start full Physics program since 1998: Routine operation 4-string stage (1996) One of the first neutrino events recorded with the 1996 four-string version NT-96 of the Telescope

17. R.Wischnewski ECRS2004 17 Photoelectrons Amplitude (Chan 12) Time difference (dt = t 52 -t 53 )  t, ns Atmospheric muons: Calibration Beam A i, t i atm.  Reconstructed  ’s : Cos(zenith) distribution vs. Corsika cos (  ) 1. 0.2

18. R.Wischnewski ECRS2004 18 Selected Results - Low energy phenomena - Atmospheric neutrinos - Neutrino from WIMP annihilation - Search for exotic particles - Magnetic monopoles - High energy phenomena - Diffuse neutrino flux - Neutrinos from GRB - Prompt muons and neutrinos

19. R.Wischnewski ECRS2004 19 Data samples NT-200 - 1998-1999: 502 livetime days (Apr.98-Feb.00) - 1998-2000: 780 livetime days (Apr.98-Feb.01) ( this work ) - 2001-2002: in progress - earlier results: for prototype NT-96,...

20. R.Wischnewski ECRS2004 20 Atmospheric Muon-Neutrinos Skyplot (galactic coordinates)  ~ 3° BG dominated bin cos (  ) Thresh. ~ 15 GeV 3-dimensional track reconstruction high BG suppression  84 events in 1998+99 Soon to come: - a high statistics neutrino sample („looser criteria“) for Point-Source Search. - Muon-Neutrino GRB analysis

21. WIMP Neutrinos from the Center of the Earth  +   b + b  W + + W - C +  +  cos (  ) Detection area, m 2 Tailored Vertical Track Reconstruction (single string)  Effective Area > 10 3 m 2 (after all cuts)

22. WIMP Search Limit on excess neutrino induced upward muon flux 90% c.l. limits from the Earth ( 502 days NT-200 livetime, E  > 10 GeV ) osc. no osc. 502 days livetime NT-200 (98+99) MC: Bartol-96 24 evts - experiment 36.6 evts - prediction w/o oscillations 29.7 evts - prediction w/ oscillations

23. R.Wischnewski ECRS2004 23 Search for fast Monopoles (  Monopole limit (90% C.L.) 780 livedays Parker N hit distribution: MC  data N hit Monopole selection criteria: hit channel multiplicity: N hit > 35 ch, upward track:  (z i -z)(t i -t)/(  t  z ) > 0.45,  o Background : atmospheric muons N  monop   = n 2 (g/e) 2 N   = 8300 N   g = 137/2, n = 1.33 Bright light source: 8300 x muon

24. R.Wischnewski ECRS2004 24 Search for Slow Massive Monopoles  (10 -5 <  -3  NT-200 – capable to detect massive bright objects (GUT-monopoles, nuclearites, Q-balls …): Monopole Trigger: N local >4 within dt=500  sec Selection: N ch >1 with N local >14 Magnetic monople Flux limit  cat         M+p M+e + (+  …),   ~10 5 Magnetic monopole visibility boundaries

25. Search for High Energy Cascades NT-200 is used to watch the volume below for cascades. 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 hit )  („BG“) NT-200 large effective volume e cascades Allowed by excellent scatt  scatt =30-50m Radius, m

26. Physics topics: - HE cascades from e   - NC/CC  Diffuse astroph.flux  GRB correlated flux - HE atmospheric muons ( the „BG“ to ‘s )  Prompt   Exotic  -... Search for High Energy Cascades NT-200 is used to watch the volume below for cascades.  („BG“) NT-200 large effective volume

27. Hard spectra pile up in the “energy parameter” N hit    AE -  Shape of signal in N hit distribution (  Selecting HE Cascades  atm 2.5  1.5 2 cut Data + MC Showers along  

28. Diffuse Flux e, ,  Limit 90% C.L. Limit via W-RESONANCE production ( E = 6.3 PeV,  5.3 ·10 -31 cm 2 ) Ф e < 4.2 · 10 -20 (cm 2 · s · sr · GeV ) -1 (Baikal 2004) Ф e < 5.0 · 10 -20 (cm 2 · s · sr · GeV ) -1 (AMANDA 2004) The 90% C.L. “all flavour” Limit from NT-200 (780 days) on the DIFFUSE NEUTRINO FLUX Assuming e     = 1  1  1 at Earth ( 1  2  0 at source) + for a  =2 spectrum Ф ~ E -2 (10 TeV < E < 10 4 TeV) E 2 Ф < 1.0 ·10 -6 GeV cm -2 s -1 sr -1 (Baikal 2004) E 2 Ф < 0.86 ·10 -6 GeV cm -2 s -1 sr -1 (AMANDA-II 2004) V geo (NT-200) AMANDA II V eff > 1 Mton at 1 PeV Effective volume vs. E

29. Experimental limits + theoretical predictions Diffuse Flux Limits + Models Models already ruled out by the experiments SDSS - Stecker et al.92 SS - Stecker, Salamon96 SP - Szabo, Protheroe92 (Models/Exp. are rescaled for 3 flavours)  Telescopes attack Models agressively.

30. R.Wischnewski ECRS2004 30 Search for ’s correlated with GRBs 1 PeV BATSE-GRBs vs. HE-Cascades event sample. April 1998 - February 2000: N tot = 722 BATSE evts NT-200: CascadeCuts (N hit >10 & t min >-10 ns) & t BATSE -100 s < t < t BATSE +100 s Data consistent with expected  at -BG  90% C.L. differential flux limits GRB - Prospects: We expect better sensitivity for the muon event sample. Analysis in progress.

31. R.Wischnewski ECRS2004 31 Prompt atmospheric ’s and muons BG source for neutrino telescopes Production - decays of short-lived particles (  D, …)      isotropic for E < 10 7 GeV Neutrinos -   e : cascades (CC, NC)  E -2.6, E<E b =3 10 5 GeV     E b 0.4 E -3, E>E b =3 10 5 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/0209111) Baikal

32. Any HE muon model spectrum can be tested by the selected HE Cascade event sample. Example: “Exotic Muons” as discussed in some talks at this meeting (curve “a” and “b”).  a detailed limit calculation for these “predictions” is in progress. The limit for E -2 spectrum shows we have rejection model power. Limits to HE Muon Flux Flux prediction and flux limits

33. Upgrade to NT-200 + Aim: Improve sensitivity to cascades with sparse instrumentation. 36 additional PMTs on 3 far ‘strings‘  4 times better sensitivity ! 1 10 100 1000 PeV 140 m 4 15 23 40 Mton

34. NT-200 + Much improved cascade coordinates (+ energy ) reconstruction

35. NT-200 + NT - 200+ as subunit for a Gton scale detector For High Energy Cascades: A single small string replacing the NT-200 central core reduces V eff less than x3 for E>100TeV.  Short strings as a subunit for a Gton scale detector 140 m

36. A future 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

37. NT-200+ Status 2004: - Two outer strings are installed 2.3 10 4 common events taken during 364 h life time (0.017 Hz) - New cable to shore (4km underwater) - DAQ system redesigned - MBit-DSL shore connection: x100 bandwidth - Embedded Linux PC’s and Ethernet underwater (fast trigger Level 0 possible) - Remote Experiment Control from Moscow/... 2005: - NT-200+ will be completed

38. R.Wischnewski ECRS2004 38 NT-200+ DAQ-Upgrade, 3/2004 Linux and Ethernet “go underwater” for the new Baikal-DAQ: - 3 Baikal-spheres with first PCs ready for deployment (left) - Mounting the central trigger/DAQ underwater system (right)

39. R.Wischnewski ECRS2004 39 Summary - The Baikal Telescope is successfully running since 10 years - strong in HE-diffuse search (cascades): “Mton-detector” - good GRB-sensitivity - relevant other results: Magnetic Monopoles, WIMPs, atm.  - complementary to AMANDA (sky, optical, pattern-reco, …) - aggressive upgrade to NT-200+ in 2005: improve the HE cascade sensitivity by 2...4 - also: ideas on a future Gigaton Volume Detector (km3)

40. R.Wischnewski ECRS2004 40 Almost exactly like our HE-Gamma colleagues we eagerly wait for more sources to show up in our field of view … At least one per Telescope … BAIKAL will for a few years remain the largest (and only) Northern hemisphere Underwater (and only) Northern hemisphere Underwater Cerenkov Telescope. Cerenkov Telescope.

41. R.Wischnewski ECRS2004 41

42. R.Wischnewski ECRS2004 42 Backup Slides...

43. WIMP Search Expectation for atmospheric neutrinos: Atm. neutrino induced muons (E th ~ 10 GeV) Atmosp. neutrinos (Bartol-96, SK-oscillation)

44. High energy cascade selection: (1)Upward light from below : t min = min(t i - t j ), j > i (for all strings in event) t min > -10 ns (2) High energy: N hit > 15 ch. Nb. of hit channels Selecting HE Cascades t min : data (N hit >40 ch.) t min : Data + MC (t min >-10 ns)

45. R.Wischnewski ECRS2004 45 Event selection criteria High energy cascades - experiment - atm. muons background

46. R.Wischnewski ECRS2004 46 Backup slides

47. R.Wischnewski ECRS2004 47 Example of interaction between ANTARES,NEMO   Baikal  Verification of Lake Baikal Attenuation / Absorb. / Scatt. results  Cross-Calibration: AC9 (Antares/Nemo) vs. Burhan ASP15 (Baikal)  Agreement ! see: NIM A498 (2003) Baikal-NEMO Campaign March, 2001

48. R.Wischnewski ECRS2004 48 Shore Station with OMs (April 1993)

49. R.Wischnewski ECRS2004 49 The end.