L/E analysis and limit on decoherence from SK

1. L/E analysis and limit on decoherence from SK I.Higuchi for SK collaboration ICRR Jul/7/2007

2. Content • Introduction • SK experiment • L/E oscillation analysis results. • L/E oscillation analysis with exotic model. • Summary

3. Introduction • We will present SK-I+II combined L/E nm ⇔ nt oscillation analysis result. And we will present test of exotic model (neutrino decoherence, neutrino decay) separately. • But, neutrino decoherence (decay) and oscillation can coexist. We can constrain decoherence (decay) parameter, if we test L/E oscillation analysis with exotic models. We report the L/E oscillation analysis with exotic models.

4. Super-Kamiokande 1996199719981999 20002001200220032004200520062007 SK-I SK-II SK-III accident reconstruction • 50kton cylindrical water Cherenkov detector(22.5kt fiducial vol.) • 1000m underground(2700m water equiv.) • optically separated into ID and OD SK-II PMT enclosure : Acrylic (front) and Fiberglass (back) SK-I 11146 Num. of inner detector PMTs 5182 40 % Photocathod coverage 19 % SK-I (1489days) + SK-II (804days) SK-III physics started in July 2006.

5. L/E oscillation analysis Dm2L Neutrino oscillation : Pmm = 1 – sin22qsin2( ) E L m Neutrino decay : Pmm = (cos2q + sin2q x exp(– ))2 2t E L 1 Neutrino decoherence : Pmm = 1 – sin22q x (1 – exp(–g0 )) 2 E Use events with high resolution in L/E The first dip can be observed • Direct evidence for oscillations • Strong constraint to oscillation parameters, especially Dm2 value

6. Reconstruction of E and L Neutrino flight length Neutrino energy En Eobserved Eobserved  En Zenith angle  Flight length Neutrino energy is reconstructed from observed energy using relations based on MC simulation Neutrino flight length is estimated from zenith angle of particle direction

7. Results of L/E oscillation analysis • SK-I+II Assuming nm⇔nt c2min= 83.9/82 d.o.f at(sin22θ,Δm2) =(1.00,2.3x10-3eV2 ) 2.0x10-3 < Dm2 < 2.8x10-3 eV2 0.93 < sin22qat 90% C.L. c2osc = 83.9/82 d.o.f c2dcy= 107.1/82 d.o.f,Dc2=23.2(4.8σ) c2dec = 112.5/82 d.o.f, Dc2 = 27.6(5.3σ) We exclude neutrino decoherece, decay about 5 s

8. L/E oscillation analysis with exotic model.

9. Dm2L Pmm = 1 – sin22qsin2( ) E Pmm = sin4q + cos4q x exp(– ) +2sin2qcos2q x exp(– ) ×cos( ) L m t E L m 2t E Dm2L Dm2L Pmm = 1 – sin22q x (1 – exp(–g0 ) ×cos( )) L 1 2E 2E 2 E oscillation and exotic mode survive probability nm⇔nt Oscillation : nm⇔ntOscillation+decay : nm⇔ntOscillation+decoherence :

10. Allowed limit at 90% C.L.: <1.4x10-22 SK-I+II Results of L/E oscillation analysis with decoherence • SK-I+II c2min = 83.8/81 d.o.f At (g0,Dm2,sin22q)= (0 GeV,2.4x10-3eV2,1.00) • 90% C.L. allowed limit: • 1.4x10-22 GeV • Improved by one order of magnitude • compared with previous limit • previous limit:2.0x10-21GeV • P.R.L. 85.1166(2000) E.Lisi, A.Marrone, • D.Montanino • Effects of decoherence on the distributions of lepton events as a function of the • zenith angle using SK-I data.

11. Results of L/E oscillation analysis with decay • SK-I+II c2min = 83.8/81 d.o.f At (m/t,Dm2,cos2q)= (0 GeV/km,2.4x10-3eV2,0.5) • 90% C.L. allowed limit: 3.2x10-5GeV/km previous best fit: 7.8x10-5GeV/km P.R.L. 82.2640(1999) V.Barger, J.G.Learned, S.Pakvasa,T.J.Wiler Effects of decoherence on the distributions of lepton events as a function of the zenith angle using SK-I data. Allowed limit at 90% C.L.: <3.2x10-5

12. summary • We reported L/E oscillation analysis with exotics. • We get c2 minimum for nm⇔nt oscillation. • SK constrains on exotics models. g0< 1.4x10-22 GeV at 90% C.L. for decoherence m/t < 3.2x10-5 GeV/km at 90% C.L. for decay

13. Back up

14. L/E resolution cut Select events with high resolution in L/E Full oscillation 1/2 oscillation Bad L/E resolution for horizontally going events  due to large dL/dcosq low energy events  due to large scattering angle D(L/E)=70%

15. L/E event summary after resolution cut SK-I 1489 days SK-II 804 days Data MC CC nm Data MC CC nm FC single-ring multi-ring stopping through-going 1619 2105.6 (98.3%) 502 813.0 (94.2%) 114 137.0 (95.4%) 491 670.1 (99.2%) 895 1140.6 (98.6%) 262 402.4 (93.6%) 64 70.7 (94.4%) 214 338.5 (99.2%) PC 2726 3725.7 Total 1435 1952.2

16. Definition of c2 Poisson with systematic errors Nobs : observed number of events Nexp : expectation from MC ei : systematic error term si: sigma of systematic error Various systematic effects in detector, flux calculation and neutrino interaction are taken into account

17. SK-I Assuming nm⇔nt c2min= 38.1/40 d.o.f at(sin22θ,Δm2) =(1.00,2.3×10-3eV2 ) SK-II Assuming nm⇔nt c2min= 45.8/40 d.o.f at(sin22θ,Δm2) =(1.00,2.4×10-3eV2 ) Results of L/E oscillation analysis • SK-I+II Assuming nm⇔nt c2min= 83.9/82 d.o.f at(sin22θ,Δm2) =(1.00,2.3×10-3eV2 ) c2osc = 83.9/83 d.o.f c2dcy= 107.1/83 d.o.f,Dc2=23.2(4.8σ) c2dec = 112.5/83 d.o.f, Dc2 = 27.6(5.3σ)

18. Combined results 2.0x10-3 < Dm2 < 2.8x10-3 eV2 0.93 < sin22qat 90% C.L.

19. Contour and Dc2 distribution Local minimum

20. Dm2L Pmm = 1 – sin22qsin2(1.27 ) E Pmm = sin4q + cos4q x exp(– ) +2sin2qcos2q x exp(– ) ×cos( ) L m t E L m 2t E Pmm = 1 – sin22q x (1 – exp(–g0 ) ×cos( )) Dm2L Dm2L Dm2L Pmm = 1 – sin22q x (1 – exp(–g0 ) ×cos( )) L L 1 1 2E 2E 2E 2 2 E oscillation and exotic mode survive probability Oscillation : Oscillation+decay : Oscillation+decoherence : I just show the upper limit. L/E analysis is not sensitive to this model. Wei-san will talk in detail. (I) (II)

21. SK-I c2min = 38.0/39 d.o.f at (g0,Dm2)= (0 GeV2,2.4x10-3eV2) Results of L/E oscillation analysis with decoherence (II) • SK-II c2min = 45.8/39 d.o.f at (g0,Dm2)= (0 GeV2,2.4x10-3eV2) • SK-I+II c2min = 83.8/80 d.o.f At (g0,Dm2)= (0 GeV2,2.4x10-3eV2) sin22q = 1.00

22. SK-I SK-II oscillation + decay contours Allowed limit at 90% C.L.: <3.2x10-5 Local minimum due to neutrino decay SK-I+II