1. 11-September-2005 C2CR2005, Prague 1 Super-Kamiokande Atmospheric Neutrino Results Kimihiro Okumura ICRR Univ. of Tokyo ( okumura@icrr.u-tokyo.ac.jp) 11-September-2005 C2CR2005, Prague

2. 11-September-2005 C2CR2005, Prague 2 Outline Super-Kamiokande-I Results new  →  oscillation analysis search for tau neutrinos search for  13 neutrino flux study Status of Super-Kamiokande-II Analysis

3. 11-September-2005 C2CR2005, Prague 3 Super-Kamiokande 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 SK-I SK-III reconstruction SK-III will start on June 2006. 50kton cylindrical water Cherenkov detector (22.5kt fiducial vol.) 1000m underground (2700m water equiv.) optically separated into ID and OD SK-I 40% Photocathod coverage 11146 Num. of inner detector PMTs SK-II accident PMT enclosure : Acrylic (front) and Fiberglass (back) SK-II 5182 19%

4. 11-September-2005 C2CR2005, Prague 4 Observation of Atmospheric Neutrino Fully Contained (E ~1GeV, e  ) Stopping  (E  ~10GeV,  ) Partially Contained (E ~10GeV,  ) Through-going  (E  ~100GeV,  ) Event classification sensitive energy: 0.1GeV ~ 10TeV

5. 11-September-2005 C2CR2005, Prague 5 Zenith Angle Distributions (SK-I) < < > >  –  oscillation (best fit) null oscillation e-like  -like FC and PC : 1489 days Up-going  : 1646 days Preliminary

6. 11-September-2005 C2CR2005, Prague 6 Previous oscillation analysis Question: Can single analysis give the best sin 2 (2  ) and  m 2 ? Zenith angle analysis : UP/DOWN ~ sin 2 (2  ) good for sin 2 (2  ) L/E analysis : dip ~ /2 good for  m 2 Allowed region of previous zenith and L/E cos  Number of events Data / MC

7. 11-September-2005 C2CR2005, Prague 7 Oscillation analysis with finer binning Important energy range to see the oscillation dip = multi-GeV Finer energy bins for multi-GeV events Important energy range to see the oscillation dip = multi-GeV Finer energy bins for multi-GeV events Full oscillation 1/2 osci. Expected sensitivity with 5yr MC (sin 2 2 ,  m 2 ) truth = (1.00, 2.5  10 -3 eV 2 ) previous zenith (180bins) L/E finer binning (370bins) zenith angle analysis with finer energy binning gives better sensitivity for both sin 2 (2  ) and  m 2

8. 11-September-2005 C2CR2005, Prague 8 Allowed region with finer binning Previous zenith-angle analysis L/E analysis 90% CL allowed region: sin 2 2  > 0.93 2.0 <  m 2 < 3.0×10 -3 eV 2 90% CL allowed region: sin 2 2  > 0.93 2.0 <  m 2 < 3.0×10 -3 eV 2 Preliminary

9. 11-September-2005 C2CR2005, Prague 9 Search for CC  events CC  events    hadrons Only ～ 1.0 CC   FC events/kton ・ yr hadrons CC  MC   appears only for up-going events  use down-going events for control sample  events are accompanied with many hadrons event topology similar to other hadronic events  likelihood (or NN) analysis

10. 11-September-2005 C2CR2005, Prague 10 Tau-like events selection criteria Visible energy > 1.33 GeV (multi-GeV energy) Multi-ring events (event w/ hadron particles) Most energetic ring is e-like (showering event) log(likelihood) > 0 or NN > 0.5

11. 11-September-2005 C2CR2005, Prague 11 Likelihood variables visible energy Max. momentum for  -like ring Clustered sphericity in the center of mass frame Max distance from primary and decay-e vertex Sphericity in the lab fame Number of candidate rings  MC Down-going data Down-going , e MC Preliminary

12. 11-September-2005 C2CR2005, Prague 12 Tau likelihood distributions downward DATA BG-MC tau-MC Cut  likelihood upward  MC) DATA BG-MC tau-MC Cut  likelihood Number of events Tau-like events : Likelihood > 0 Preliminary

13. 11-September-2005 C2CR2005, Prague 13 Likelihood analysis NN analysis , e, & NC background Data ×1.82  MC ×1.93  MC cos  zenith Number of events 145±48(stat) +9 / -36 (osc. para. uncertainty) 152±47(stat) +12 / -27 (osc. para. uncertainty) 79±31(syst) Fitted # of  events Expected # of  events Preliminary Zenith angle dist. and fit results

14. 11-September-2005 C2CR2005, Prague 14 Search for non-zero  13 Non-zero  13 will enhance   → e oscillation in multi-GeV energy due to matter effect in Earth Electron appearance is expected in upward-going events s 2 13=0.05 s 2 13=0.00 null oscillation Electron appearance 1+multi-ring, e-like, 2.5 - 5 GeV P(  → e) cos  zenith Neutrino Energy (GeV) cos  zenith Three flavor oscillation analysis with  m 2 solar =0 assumption :

15. 11-September-2005 C2CR2005, Prague 15 Multi-GeV electrons Multi-GeV electrons UP/DOWN asymmetryZenith angle single-Ring electron multi-Ring electron Preliminary No significant excess due to matter effect in upward-going multi-GeV electron sample Data No oscillation Three flavor best fit (normal hierarchy)

16. 11-September-2005 C2CR2005, Prague 16 Allowed region for  13 Distributions are best fitted when sin 2 (  13 )=0 Consistent with two flavor     oscillation sin 2 (  13 )<0.14 allowed in 90% C.L. from SK-I data Normal hierarchy (  m 2 >0)  2 min /ndf = 376.82/368 @(2.5x10 -3, 0.5, 0.0) Preliminary 90%CL 99%CL excluded by CHOOZ  m 2 (eV 2 ) sin 2  13 sin 2  23 sin 2  13

17. 11-September-2005 C2CR2005, Prague 17 Atmospheric flux measurement Recent neutrino flux calculations have improved due to accurate measurement of comic-ray protons / muons Approximately 20% difference still exists among flux models in higher energies Neutrino flux calculation cosmic-ray proton flux 

18. 11-September-2005 C2CR2005, Prague 18 e and  energy spectrum e and  energy spectrum SK-I  e and  event rates are compared with expectation in each energy range Neutrino energies are estimated from simulation Neutrino oscillation included for  expected  →   (  m 2, sin 2 2  ) = (2.5x10 -3 eV 2,1.0) assumed expectation data sub-GeV multi-GeV sub-GeV multi-GeV PC upmu-stop upmu-thru Events / yr / GeV Neutrino energy  (GeV) e  Preliminary

19. 11-September-2005 C2CR2005, Prague 19 Comparison with flux models Neutrino flux models: HKKM04 Phys. Rev. D70 043008 (2004) Bartol Phys. Rev. D70 023006 (2004) Fluka hep-ph/0305208 Systematic uncertainties: detector efficiency cross section ~10% oscillation ~4% for  Results: absolute flux and spectrum are consistent within systematic errors HKKM04 and Fluka under- estimated high energy  flux Data / Expectation e  Preliminary Error bar :  (stat.) 2 +(sys.) 2

20. 11-September-2005 C2CR2005, Prague 20 New HKKM flux calculation HKKM flux revised: modified hadron interaction model see Dr. Honda’s talk Agreement in high energy  becomes better Data / Expectation e  Preliminary Error bar :  (stat.) 2 +(sys.) 2

21. 11-September-2005 C2CR2005, Prague 21 Zenith Angle Distributions (SK-II) < < > >  –  oscillation (best fit) null oscillation e-like  -like FC and PC : 627 days Up-going  : 609 days Preliminary

22. 11-September-2005 C2CR2005, Prague 22 Preliminary Contours for SK-II SK-IISK-I SK-II data are consistent with SK-I data SK-I + SK-II combined analysis : next step

23. 11-September-2005 C2CR2005, Prague 23 SK-II L/E analysis L/E analysis was carried out for the SK-II data with the identical selection criteria as those in SK-I. SK-II SK-I Osc. Decay Decoh. Consistent with SK-I. Oscillation still gives the best fit to the data. Consistent with SK-I. Oscillation still gives the best fit to the data. Preliminary

24. 11-September-2005 C2CR2005, Prague 24 Summary SK-I analysis results: New  →  oscillation analysis with finer binning gives more stringent constraint : sin 2 2  > 0.93, 2.0<  m 2 <3.0x10 -3 eV 2 (90%C.L.) Data are consistent with  appearance No evidence for multi-GeV electron appearance due to non-zero  13 Neutrino flux calculation models are compared and consistent with data SK-II data was analyzed independently and consistent with SK-I

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