1. Super-Kamiokande Introduction Contained events and upward muons Updated results Oscillation analysis with a 3D flux Multi-ring events  0 /  ratio 3 decay Search for  leptons   s Conclusion Y.Totsuka Kamioka

2. Super-Kamiokande collaboration

3. Super-Kamiokande detector 50,000 ton water Cherenkov detector (22.5 kton fiducial volume) 1000m underground (2700 m.w.e.) 11,146 20-inch PMTs for inner detector 1,885 8-inch PMTs for outer detector

4. Atmospheric neutrinos p, He...  , K   ee  e L=10-30 km L=up to 13000 km    e  e = ~ 2    e  e @ low energy (E  GeV) @ high energy Neutrino oscillations :     e e dataMC 11 Error in absolute flux~20%, but  / e ratio~5%     e e

5. Atmospheric neutrino spectrum Energy dependence of   e ratio <5% accuracy       e   e        e   e (3-D) (P.Lipari)

6. Primary cosmic ray flux protons He From P.Lipari

7. Bartol and Honda fluxes

8. Zenith angle distribution(1D) For E  > a few GeV, Upward / downward = 1 (within a few %) Up/Down asymmetry for neutrino oscillations Calculated zenith angle distribution E =0.5GeVE =3GeVE =20GeV

9. p p 1D p p 3D 3D calculation by G.Battistoni et al. (hep-ph/9907408)  10 -3 –0.2 GeV0.2-0.5 GeV 0.5-1 GeV1-5 GeV horizontalvertical 3D neutrino flux calculation

10. Contained events Interaction in the rock Upward through- going muons contained through-going muons stopping muons Upward stopping muons Initial neutrino energy spectrum How to detect atmospheric neutrinos

11. Contained event analysis e or  Fully Contained (FC)Partially Contained (PC)  No hit in Outer DetectorOne cluster in Outer Detector Reduction Automatic ring fitter Particle ID Energy reconstruction Fiducial volume (>2m from wall, 22 ktons) E vis > 30 MeV (FC), > 3000 p.e. (~350 MeV) (PC) Final sample: FC: 8.2 ev./day, PC: 0.58 ev./day E vis < 1.33 GeV : Sub-GeV E vis > 1.33 GeV : Multi-GeV

12. Total 754 1065.0 Data MC(Honda flux) 1ring e-like 626 612.8  -like 558 838.3 Multi ring 1318 1648.1 Total 2502 3099.1 Sub-GeV (Fully Contained) E vis 100 MeV, P   > 200 MeV Data MC(Honda flux) 1ring e-like 2864 2667.6  -like 2788 4072.8 Multi ring 2159 2585.1 Total 7811 9325.5  /e Data  /e MC = 0.638  0.050 Multi-GeV Fully Contained (E vis > 1.33 GeV) Partially Contained (assigned as  -like)  /e Data  /e MC = 0.675 +0.034 -0.032  0.080 (1289.4 d (79.3 kt.  y))  0.017 Fully contained event summary

13. Zenith angle distribution 1289 days (79.3 kt. yrs) No oscillation Best fit (  m 2 =2.4x10 -3 eV 2, sin 2 2  =1.00)  2 (best fit) = 132.4/137 d.o.f.  2 (no osc.) = 299.3/139 d.o.f.  2 =167 (E<1.33 GeV) (E>1.33 GeV)

14. Multi-ring event analysis 1289 days (79.3 kt. yrs) No oscillation Best fit (  m 2 =2.0x10 -3 eV 2, sin 2 2  =1.00) Sub-GeV muti-ring  -like sample Zenith angle distributions Multi-GeV muti-ring  -like sample 0.6 GeV < E < 1.33 GeV E > 1.33 GeV The zenith angle distortion is consistent with single-ring analysis. preliminary cos 

15. Upward through-going muons horizontalvertical No oscillation:  2 (shape)=18.7 / 10 d.o.f. (prob.=0.044) Osc. best fit (  m 2 =5.2x10 -3 eV 2,sin 2 2  =0.86) Upward stopping muons No oscillation: (Bartol, GRV94) Oscillation (  m 2 =3.2x10 -3 eV 2,sin 2 2  =1.00) stopping  through  ( ) Data stopping  through  ( ) MC = 0. .016 +0.013 - 0.011 0.368 +0.049 - 0.044 0. . .09 = << 1 1416 events / 1268 days 345 events / 1247 days Zenith angle distributions of upward-going muons

16. 79.3 kt. yrs    Best fit :  m 2 =2.5x10 -3 eV 2, sin 2 2  =1.00 (  2 =142.1 / 152 d.o.f.) 68% C.L. 90% C.L. 99% C.L. SK combined result  m 2 = (1.7~4)x10 -3 eV 2 sin 2 2  > 0.89 (90% C.L.) Allowed region (FC + PC + UP-thru + UP-stop)

17. 79.3 kt. yrs    Best fit :  m 2 =2.5x10 -3 eV 2, sin 2 2  =1.00 (  2 =142.1 / 152 d.o.f.) 68% C.L. 90% C.L. 99% C.L. SK combined result  m 2 = (1.7~4)x10 -3 eV 2 sin 2 2  > 0.89 (90% C.L.)  m 2 (eV 2 ) sin 2 2  unphysical region Allowed region - II (FC + PC + UP-thru + UP-stop)

18. No oscillation Best fit (  m 2 =2.5x10 -3 eV 2, sin 2 2  =1.00) Zenith angle distributions for the best fit

19. Allowed region (grand global fit) (FC + PC + UP-thru + UP-stop + multi-rings) 79.3 kt. yrs Within physical region; x 2 min = 157.5/170 dof at sin 2 2  = 1.0,  m 2 = 2.5  10 -3 eV 2 With unphysical region; x 2 min = 157.4/170 dof at sin 2 2  = 1.01,  m 2 = 2.5  10 -3 eV 2

20. Zenith angle distributions for the best fit (grand global fit) No oscillation Best fit (  m 2 =2.5x10 -3 eV 2, sin 2 2  =1.00)

21. Zenith angle distributions for the best fit (cont) (grand global fit) No oscillation Best fit (  m 2 =2.5x10 -3 eV 2, sin 2 2  =1.00)

22. Systematics in the 1D fit

23.   sterile (  0 method) (   /  ) Data (   /  ) MC > 1 for     1 for   s Data 355.2 events (BG subt.) MC 323.2 events (   /  ) Data (   /  ) MC = 1.49  0.08(stat.)  0.11(sys.) { Experimental only

24.  0 info from K2K-1kt  0 FC-  () data = 0.99  0.03  0.1 PRELIMINARY  0 FC-  () MC

25. (  0 /  ) data vs (  0 /  ) MC-no-osc PRELIMINARY

26. Using matter effect and enriched NC sample    : No matter effect   s : With matter effect Neutrino oscillation in matter:  () = ( cos  m s sin  m - sin  m cos  m ) 1 2 () sin 2 2  m sin 2 2  = (  cos2    sin 2 2   =  2 G F n n E /  m 2  For sin 2 2  =  1 sin 2 2  m 1 ~    + 1 And for E = 30~100 GeV    1 and sin 2 2  m   1 Suppression ! Strategy: Obtain allowed region using lower energy events (Fully contained sample) Then, Test zenith angle of NC enriched events, high energy PC and through-going muon events.   sterile (matter in earth)

27. Allowed region using only FC events

28. Zenith angle of upward-going muon  m 2 = 3 x10 -3 eV 2 sin 2 2  = 1  m 2 = 3 x10 -3 eV 2 sin 2 2  = 1   s    > 45000 p.e. (E> ~ 5 GeV) =~25 GeV   s Zenith angle of high energy PC events

29.   s    Criteria > 400 MeV visible energy Multi-ring event e-like ring is the most energetic ring Contents NC : 29 % e CC : 46 %  CC : 25 %  m 2 = 3 x10 -3 eV 2 sin 2 2  = 1 Zenith angle of NC enriched events

30.   s    sin 2 2  = 1   s      s    Up/Down ( cos  ) ratio of NC enriched multi-ring Up/Down (cos  ) ratio of High Energy PC Vertical/Horizontal ratio (cos  -0.4) of up muons Data 10 -3 10 -2 eV 2 10 -3 10 -2 eV 2 Ratios vs.  m 2 > < > 0.4 <-0.4 > 0.4

31. combine NC enriched, high E PC and up muons   s is excluded with 99 % C.L. excluded Allowed vs. excluded regions

32. Neutrino CC cross sections  CC Signature of  appearance:  + N   + N’ +  +   CC Expected  events  Higher multiplicity of Cherenkov rings  More  e decay signals  More spherical event pattern  e  hadrons(  Search for  appearance (3 methods) : (1) Energy flow and event shape analysis (2) Likelihood method using # of rings,  e, max p.e. ring and etc. (3) Neural network method Each method is optimized using only downward going events and then looks at upward going events. (I.e. blind method to disable systematic bias.) All cos  <-0.2 cos  >0.2 ~20ev./yr for 3x10 -3 eV 2 sin 2 2  = 1 E (GeV)  m 2 (eV 2 ) Search for  leptons

33. Multi-ring samples : atm  + e w/o  :  CC

34. All methods show ~2  excess of  -like events. The result is consistent with    oscillations. MC with  MC without  Likelihood method Observed # of  : 27 +9 -8  m 2 =3x10 -3 eV 2, sin 2 2  =1.00 (expected # of  : 74 events) Efficiency for  : 43.5 % # of  production: 62 -18 +39 Energy flow method +14 -13 Efficiency for  : 32 % # of  production: 79 -40 Observed # of  : 25.5 cos  Neural network method Observed # of  : 42  19 +13 -13 # of  production: 92  35.3 -0 +44 +14 Efficiency for  : 45 % +17 -16 -27 +21 Zenith-angle distribution

35. Test    oscillation with : P(    )=sin 2 2  sin 2 (  L  E n ) (  n : parameters) Use FC, PC, Up-through, and Up-stop data n=-1 is the standard neutrino oscillation index n 22 -201 Magnified view n = -1.06  0.14 Probability of exotic oscillation models

36. Neutrino decay Let neutrinos oscillate and decay 3 X(invis); P(   ) = sin 4  + cos 4  exp ( ) + sin 2  exp ( ) cos ( ) Consider two cases; dcy>> osc, and dcy<< osc, where dcy =, osc = m 3 L  3 E m 3 L 2  3 E  m 2 L 2E  3 E m 3 4  E  m 2

37. dcy >> osc For  m 2 ,  2 min = 221.2/153 dof Bad fit !

38. dcy << osc For  m 2 0,  2 min = 147.1/153 dof at (sin 2 , m 3 /  3 ) = (0.68, 0.01 (GeV/km)) Good fit !

39. Up/down of NC enriched events (short dcy ) FC, Nring>1, Evis>400MeV, Brightest ring = e-like Allowed from FC+PC+Upmu Excluded from NC The case of dcy << osc is disfavored

40. Conclusions on atmospheric neutrinos Oscillation parameters for    :  m 2 = 1.7 ~ 4 x 10 -3 eV 2, sin 2 2  > 0.89 (90%CL) 3D flux does not change the conclusion but more precise 3D calculations are needed   s is strongly disfavored  0 /  ratio is consistent with    Excess from  leptons ~ 2  Decay senario is disfavored with > 2  for dcy >> osc and dcy << osc