1. The AMANDA-II Telescope - Status and First Results - Ralf Wischnewski / DESY-Zeuthen for the AMANDA Collaboration ralf.wischnewski@desy.de TAUP2001, September 2001, LNGS/Italy

2. HE ’ Telescopes … HE -Telescopes are still ”novel” instruments proving sensitivity to their primary channels   N   X e N  e X  from Astrophysical Sources ( Point / Diffuse )  calibration possible only with atmospheric ‘s

3. Outline 1. AMANDA-II Detector 2. Calibration of the AMANDA-B10 detector with Atmospheric ‘s  Physics results from B10/1997, see A.Hallgren 3. Performance & Sensitivity of AMANDA-II

4. AMANDA-II Construction 1996 4 strings, coax transmission OMs total 86 OMs  AMANDA-B4 1997 +6 strings, twisted pair transmission OMs total 302 OMs at 10 strings  AMANDA-B10 1998 +3 strings, fiber transmission OMs total 424 OMs  AMANDA-B13 2000 +6 strings, fiber and digital transmission OMs total 677 OMs at 19 strings  AMANDA-II 2003 - 2008 ~80 strings with 60 OMs each, total 5000 OMs  ICECUBE

5. 677 PMTs 19 Strings d = 200 m h  500 m  V geo  1.6 10 7 m 3 AMANDA-II (February 2000) Trigger: Majority >23 OM in <2.5  s String Trigger

6. Atmospheric Muon Background  from atm.  from CR Zenith of  ‘s triggering AMANDA -Signature: Upgoing muon Background: Misreconstructed atmospheric muons Noise/Signal =   /   ( atm ) = 10 5…6

7. Maximum Likelihood Reconstruction Variation of track parameters until the spectrum of arrival times has highest Likelihood. Scattering results in a distance dependent time- delay relative to the Cherenkov cone.

8. Atmospheric -Analysis Two (largely) independent analyses were done for the 1997 data set of Amanda-B10 with respect to - methodical aspects (Cut definitions, minim.functional) - data cleaning (electronic noise...) Used same signal & atmospheric muon Background MC (BG-MC) and track model (ice optics and single muon)

9. Analysis A: Overview Conventional Likelihood description (no zenith weight) Multi-photon Likelihood and hit-probabilities Background rejected by specific cuts: e.g. cascade fit for muon bremsstrahlung. Reject instrumental BG by hit-topology Cuts developed with emphasis on BG-MonteCarlo Deterministic method to define a small set of final Cut parameters and their values (  CutEval)

10. N events  bg  sig S/N Pre-processing : 1 10 9 0.950.951 : 2 10 5 Hit cleaning, Calibration... Level 1: 5 10 7 5 10 -2 0.371 : 3 10 4 Fast track approximation (line fit) Simple up/down cut Level 2:4 10 5 4 10 -4 0.151 : 5 10 2 Time-likelihood reconstruction. Simple cuts (zenith,L,Ndir) Level 3:1 10 4 1 10 -5 0.071 : 30 First cut optimization. Full likelihood reconstruction. Level 4: 223 2 10 -8 0.0410 : 1 Final Neutrino Cuts (CutEval) Neutrino Analysis Chain (A)

11. Analysis A: Neutrino Cuts & Sample Size Sample Quality, Q Define „Sample Quality“: Q = -log (N BG /N TL ) Find (minimum) set of Cut- Variables, which optimize the signal to background efficiency Data BG-MC Sig-MC

12. Neutrino Events – Statistics 130.1 days live time

13. Systematic Uncertainties Calibration Time Geometry Amplitude OM sensitivity Bulk Ice Vertical structures Hole Ice Optical properties Physics  -prop./light yield -flux -oscillations ± 30 % ± 20 % -20 % ± 10 % < 5 % - 5 % -50 % -20 %

14. - Luminosity versus day in 1997 Number of Neutrino events and total number of triggers in 1997 (analysis A). Total live time was 130.1 days. Neutrino candidates Nb. of trigger (Mill.)

15. Zenith angle distribution Analysis A Cos(zenith) Events /130d /0.1

16. Energy distribution 10 GeV100 GeV1000 GeV (MC) E ~.07–3.4 TeV

17. Celestial distribution Combined sample 325 events 130.1 days live-time Pointing: 3 ª - 4 ª No clustering

18. Oscillations:Zenith dependence (MC) Cos(zenith) Events /130d /0.05 Ratio Osci/No oscci

19. Oscillations: Neutrino Energy (MC)

20. Summary: B-10 atmosph. ’s The AMANDA-B data from 1997 (130.1 days live time) have been analysed for neutrino induced events 2 independent analyses find a total of 325 neutrino events with less than 10% background contamination Results are consistent with the MC expectation for background (atmospheric muons) and signal (atmospheric neutrinos) within (still relatively large) systematic uncertainties Improvement expected from - better local ice-properties & OM sensitivity calibration - improved MC light tracing & HE muon light yield AMANDA has reached „design luminosity“ !

21. Larger effective area by 9 more strings (>double OMs) New technologies - improved timing - MultiHit resolution (muon bundles & HE events) - reduced electronic noise - Upgrade: full waveform sampling (FADCs) in 2002 Triggering - HE events by majority trigger - E<100 GeV by string trigger - EAS-Array (SPASE) as efficient veto for UHE events Improved angular sensitivity range; resolution ~ 2 degrees Amanda-II

22. Amanda-II analysis for 2000 started in spring 2001 (1.2 TB Data back from Spole) Neutrino Analysis profits substantially from Amanda-B10 analysis. Tuning to new geometry and hardware is under way. Minimum bias and low neutrino-cut level data look ok vs. MC. MC-results given below for „final AM-II neutrino cuts“ (A eff,,...) are still preliminary. Amanda-II

23. Amanda-II: Detector response Number of hit Optical Modules Inner Strings (1-10) All Strings (1-19) Outer Strings (11-19) Data - dots MC - line

24. Amanda-II: Detector response Minimum bias Zenith & Azimuth acceptance

25. Event Rates:  and  e Trigger Level Atmospheric  - 11000 (CC) - 130 (NC) e - 160 (CC) - 9 (NC) AGN (E -2 10 -6 GeVcm - 2 s - 1 sr -1 )  - 853 (CC) e - 103 (CC)  e ATM AGN

26. Atmospheric  MC: Energy response After BG rejection A eff (E) much improved compared to AMANDA-B10 Trigger Level

27. Atmosph.  MC: Angular Sensitivity Trigger Level After BG rejection uphorizon Nearly uniform angular sensitivity to horizon ~200 atm per angular bin & livetime-year

28. AMANDA-II: a horizontal  event ( preliminary Am-II neutrino  - cuts )

29. Am-II: Effective Area vs zenith A eff depends sensitively on the physics objective! Point source sensitivity is uniform to near horizon

30. Amanda-II - Effective Volume V eff (  ) is 0.3-0.5 km 3 R  > 10 km (for Point Source Cuts)

31. Diffuse Flux  AGN Core Convolved energy resolution New techniques Anticipated sensitivity

32. AMANDA-II Anticipated sensitivity Upper Bounds on Diffuse Flux Baikal NT-200

33. Point Sources Atmospheric  + energy resolution

34. Point Sources Focus on Mk501 as example

35. Earth shadowing of ‘s becomes relevant for    PeV Horizontal and „downgoing“ events dominate New search strategies under development - Total energy cuts & Energy flow vs. track reconstruction - EAS-Veto by surface Array SPASE UHE events

36. Downgoing -induced MuonFlux

37. Angular distribution Down Up Most events are horizontal. EeV sources cut off very quickly below horizon. Direction provides additional BG reject.

38. Summary AMANDA-B10 Final Analysis (1997) yields 325 HE neutrino events The first high statistics -event sample for an UWater/Uice Telescope Proof of principle of operation in Antarctic scattering ice. AMANDA-II >10 5 m 2 Trigger Area - the Largest Muon and Neutrino Telescope ever built. Improved performance compared to B10-Telescope Horizontal Angular acceptance Event rates of 4-5 atm. ‘s per livetime day, 800-1000 ‘s for year-2000.