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Super-Kamiokande

Super-Kamiokande. Y.Totsuka Kamioka. Introduction Contained events and upward muons Updated results Oscillation analysis with a 3D flux Multi-ring events p 0 / m ratio n 3 decay Search for t leptons n m  n s Conclusion. Super-Kamiokande collaboration. Super-Kamiokande detector.

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Super-Kamiokande

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  1. Super-Kamiokande Y.Totsuka Kamioka • Introduction • Contained events and upward muons • Updated results • Oscillation analysis with a 3D flux • Multi-ring events • p0/m ratio • n3 decay • Search for t leptons • nmns • Conclusion

  2. Super-Kamiokande collaboration

  3. Super-Kamiokande detector 50,000 tonwater 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. n + n m m n + n e e n n + + n n m m m m n n + + n n e e e e p, He ... Atmospheric neutrinos L=10-30 km p , K e nm nm ne L=up to 13000 km @ low energy (En < 1 GeV) = ~ 2 n + n m m @ high energy n + n e e Error in absolute flux~20%, but nm/ne ratio~5% Neutrino oscillations : 1 d a t a M C

  5. pmnm enmne pm nm e nmne (P.Lipari) Atmospheric neutrino spectrum (3-D) Energy dependence of nm/ne ratio <5% accuracy

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

  7. Bartol and Honda fluxes

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

  9. 3D neutrino flux calculation p p 1D 3D p p n n n n 3D calculation by G.Battistoni et al. (hep-ph/9907408) nm 10-3–0.2 GeV 0.2-0.5 GeV 0.5-1 GeV 1-5 GeV horizontal vertical

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

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

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

  13. 1289 days (79.3 kt . yrs) No oscillation Zenith angle distribution Best fit (Dm2=2.4x10-3eV2, sin22q=1.00) (E<1.33 GeV) (E>1.33 GeV) c2(best fit) = 132.4/137 d.o.f. c2(no osc.) = 299.3/139 d.o.f. Dc2=167

  14. 1289 days (79.3 kt . yrs) Zenith angle distributions preliminary Multi-ring event analysis No oscillation Best fit (Dm2=2.0x10-3eV2, sin22q=1.00) Sub-GeV muti-ring m-like sample 0.6 GeV < E < 1.33 GeV cosq Multi-GeV muti-ring m-like sample E > 1.33 GeV cosq The zenith angle distortion is consistent with single-ring analysis.

  15. Zenith angle distributions of upward-going muons Upward through-going muons 1416 events / 1268 days No oscillation: c2(shape)=18.7 / 10 d.o.f. (prob.=0.044) Osc. best fit (Dm2=5.2x10-3eV2,sin22q=0.86) vertical horizontal Upward stopping muons ) ( stoppingm 345 events / 1247 days throughm Data ) ( stoppingm throughm MC No oscillation: (Bartol, GRV94) +0.013 0.241  0.016 - 0.011 = 0.368 +0.049 - 0.044 = 0.65  0.04  0.09 << 1 Oscillation (Dm2=3.2x10-3eV2,sin22q=1.00)

  16. Allowed region (FC + PC + UP-thru + UP-stop) nmnt 79.3 kt . yrs Best fit : Dm2=2.5x10-3eV2, sin22q=1.00 (c2=142.1 / 152 d.o.f.) 68% C.L. 90% C.L. 99% C.L. SK combined result Dm2 = (1.7~4)x10-3eV2 sin22q > 0.89 (90% C.L.)

  17. Allowed region - II(FC + PC + UP-thru + UP-stop) nmnt 79.3 kt . yrs Best fit : Dm2=2.5x10-3eV2, sin22q=1.00 (c2=142.1 / 152 d.o.f.) unphysical region Dm2 (eV2) 68% C.L. 90% C.L. 99% C.L. sin22q SK combined result Dm2 = (1.7~4)x10-3eV2 sin22q > 0.89 (90% C.L.)

  18. Zenith angle distributions for the best fit No oscillation Best fit (Dm2=2.5x10-3eV2, sin22q=1.00)

  19. Allowed region (grand global fit)(FC + PC + UP-thru + UP-stop + multi-rings) 79.3 kt . yrs Within physical region; x2min = 157.5/170 dof at sin22q = 1.0, Dm2 = 2.510-3 eV2 With unphysical region; x2min = 157.4/170 dof at sin22q = 1.01, Dm2 = 2.510-3 eV2

  20. Zenith angle distributions for the best fit(grand global fit) No oscillation Best fit (Dm2=2.5x10-3eV2, sin22q=1.00)

  21. Zenith angle distributions for the best fit (cont)(grand global fit) No oscillation Best fit (Dm2=2.5x10-3eV2, sin22q=1.00)

  22. Systematics in the 1D fit

  23. nmnsterile(p0 method) (p0/m)Data { > 1 for nmnt  1 for nmns (p0/m)MC Data 355.2 events (BG subt.) MC 323.2 events (p0/m)Data = 1.49 0.08(stat.) 0.11(sys.) (p0/m)MC Experimental only

  24. p0 info from K2K-1kt ( ( ) ) p0 FC-m p0 FC-m data MC = 0.99  0.03  0.1 PRELIMINARY

  25. (p0/m)data vs (p0/m)MC-no-osc PRELIMINARY

  26. nmnsterile (matter in earth) Using matter effect and enriched NC sample nmnt : No matter effect nmns : With matter effect Neutrino oscillation in matter: ( ) ( ) ( ) cosqm nm sinqm n1 = ns - sinqm cosqm n2 sin22q sin22qm = (z-cos2q)2+sin22q z = - 2 GFnnEn / Dm2  1 sin22qm ~ For sin22q = ~ 1 z2+ 1 And for En = 30~100 GeV z>>1 and sin22qm<<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.

  27. Allowed region using only FC events

  28. Zenith angle of high energy PC events > 45000 p.e. (E> ~ 5 GeV) <E>=~25 GeV nmns nmnt Dm2 = 3 x10-3eV2 sin22q = 1 Zenith angle of upward-going muon nmns Dm2 = 3 x10-3eV2 sin22q = 1 nmnt

  29. Zenith angle of NC enriched events nmnt nmns Criteria > 400 MeV visible energy Multi-ring event e-like ring is the most energetic ring Contents NC : 29 % ne CC : 46 % nm CC : 25 % Dm2 = 3 x10-3eV2 sin22q = 1

  30. Ratios vs. Dm2 sin22q = 1 nmnt <-0.4 Up/Down ( cosQ ) ratio of NC enriched multi-ring > 0.4 Data nmns nmns nmns Data Data nmnt nmnt 10-3 10-2 eV2 10-3 10-2 eV2 <-0.4 Up/Down (cosQ ) ratio of High Energy PC > 0.4 Vertical/Horizontal ratio (cosQ -0.4) of up muons > <

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

  32. Search for t leptons Neutrino CC cross sections Expected t events sin22q = 1 ~20ev./yr for 3x10-3 eV2 nm CC All nt CC cosq<-0.2 En(GeV) Signature of t appearance: nt + N  t + N’ + p + p ..... Dm2(eV2) cosq>0.2 mnn, enn, n+hadrons(p,p,....) • Higher multiplicity of Cherenkov rings • More me decay signals • More spherical event pattern Search for t appearance (3 methods) : (1) Energy flow and event shape analysis (2) Likelihood method using # of rings, m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.)

  33. Multi-ring samples : atm nm + ne w/o nt : ntCC

  34. Zenith-angle distribution MC without t Dm2=3x10-3eV2, sin22q=1.00 (expected # of t : 74 events) MC with t Energy flow method +14 Observed # of t : 25.5 -13 Efficiency for t: 32 % +44 # of t production: 79 -40 Likelihood method +17 +9 Observed # of t : 27 -8 -16 Efficiency for t : 43.5 % +39 +21 # of t production: 62 -27 -18 Neural network method +13 Observed # of t : 42 19 -13 Efficiency for t : 45 % +14 # of t production: 92 35.3 -0 cosq All methods show ~2s excess of t-like events. The result is consistent with nmnt oscillations.

  35. Probability of exotic oscillation models Test nmnt oscillation with : P(nmnt)=sin22q sin2(bLEn) (q, b, n : parameters) n=-1 is the standard neutrino oscillation Use FC, PC, Up-through, and Up-stop data c2 -2 -1 0 1 Magnified view index n n = -1.06  0.14

  36. Neutrino decay m3 L t3 E Dm2 L 2E m3 L 2t3 E 4pE Dm2 Let neutrinos oscillate and decay n3 X(invis); P(nmnm) = sin4q + cos4q exp() + sin2q exp() cos() Consider two cases; ldcy>>losc, and ldcy<<losc, where ldcy = , losc = t3E m3

  37. ldcy >>osc For Dm2, c2min = 221.2/153 dof Bad fit !

  38. ldcy << losc For Dm2 0, c2min = 147.1/153 dof at (sin2q, m3/t3) = (0.68, 0.01 (GeV/km)) Good fit !

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

  40. Conclusions on atmospheric neutrinos • Oscillation parameters for nm nt : Dm2 = 1.7 ~ 4 x 10-3 eV2, sin22q > 0.89(90%CL) • 3D flux does not change the conclusion but more precise 3D calculations are needed • nm ns is strongly disfavored • p0/m ratio is consistent with nm nt • Excess from t leptons ~ 2s • Decay senario is disfavored with > 2sfor ldcy>>losc and ldcy<<losc

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