Recent Results from Super-Kamiokande on Atmospheric Neutrino MeasurementsChoji Saji ICRR,Univ. of Tokyo for the Super-Kamiokande collaborationICHEP 2004, BeijingContentsAtmospheric neutrino oscillation studies using full Super-Kamiokande I(SK-I) data nm nt oscillation analysis L/E analysis 3-flavor analysisStatus of Super-Kamiokande II(SK-II)

Atmospheric neutrinoseeDownwardL=10~100 kmUpwardL=up to 13000 kmUp/Down SymmetryZenith angle dist. of Atmospheric n flux En > a few GeVcosq

Atmospheric neutrinos in Super-Kamiokande

2-flavor oscillation analysisExpectation- Three dimensional (3D) n flux calculation - interaction parameters (tuned by K2K data)Treatment of systematic errors in c2 calculationEach systematic error source is treated as independent error term(39 error terms)Data set: full SK-I (FC,PC 1489days, up- 1646 days)Improvements:

Zenith angle distributions~15km ~13000km~500km~13000km~500kmBest fit sin22q=1.0, Dm2=2.1x10-3 eV2Null oscillation

Oscillation Analysis ResultsBest fit:sin22 =1.0m2 = 2.1x10-3 eV2 2 = 175.2/177 dof90% C.L. region:sin22 > 0.921.5 < m2 < 3.4x10-3 eV2(FC + PC + UP-m)Full paper will be soon0.70.80.910.750.850.9510-310-2

L/E Analysis Expand fiducial volume(FC)need more statisticsSelect events with high resolution in L/E DL/E < 70%FC(single, multi-ring) m-likePCA first dip should be observed Direct evidence for oscillations Strong constraint to oscillation parameters, especially Dm2 value FC single-ringFull oscillation1/2 oscillationD(L/E)=70%

L/E DistributionNull oscillation MC1489.2 days FC+PCFirst dip is seen as expected by neutrino oscillationBest fit expectation w/ systematic errorsMostly downwardMostly upward

L/E SignificanceThe first dip of the data cannot be explained by other modelsDc2 (n decay n oscillation) =11.4 3.4 sDc2 (n decoherence - n oscillation) =14.6 3.8 s

L/E Oscillation resultDm2=2.4x10-3,sin22q=1.00c2min=37.9/40 d.o.f(sin22q=1.02, c2min=37.7/40 d.o.f)

1.9x10-3 < Dm2 < 3.0x10-3 eV20.90 < sin22q @ 90% C.L.Strong constraint on Dm2

3-flavor OscillationP(negnm ) = sin2(2q13) x sin2q23 x sin2(1.27Dm2L/E) P(nmgnt) = cos4q13 x sin2(2q23) x sin2(1.27Dm2L/E)P(negne) = 1 - sin2(2q13) x sin2(1.27Dm2L/E)assuming Dm212 = 0eV2 3 parameters; Dm223= Dm213, q13, q23 neutrino oscillation probabilities are described as;Oscillation probabilitymatter effectlog10(E(GeV))P(nene)( cosQ=-0.6)

3-Flavor Analysis resultnormalinvertedBestfit: Dm2 = 2.7x10-3ev2, sin2q23 = 0.5, sin2q13 = 0.0no evidence for non zero q13m3m2m1m3m2m1sin2q23sin2q13Dm2sin2q13(preliminary)

SK - II

Preliminary!Status of SK-II Atmospheric NeutrinosSK-II event 311.5days data (preliminary) SK-II data are consistent with SK-I Clear deficit in upward nm

ConclusionSK-II analysis is in progress - preliminary data are consistent with SK-I oscillation SK-I full data set (FC,PC 1489days, up- 1646days) Improved MC prediction and oscillation analysis allowed region @ 90% C.L. 1.5 < m2 < 3.4x10-3 eV2, sin22 > 0.92 SK-I final result will be published soonL/E analysis Evidence for oscillatory signature 1.9 < Dm2 < 3.0x10-3 eV2, sin22q > 0.90@90%C.L.3 - flavor oscillation - no evidence for non zero q13SK-I analysis

Supplements

CPT VIOLATION

2-flavor

Calculation methods, basic idea(based on Fogli et al., hep-ph/0206162)In our current analysis, minimum 2 is obtained by optimizing j (j = 1,2,..) for each (sin22,m2) point. 2 is minimum for any j .But, mathematically,Minimizing 2Solving nsys linear equation.2-flavor

Sub-Sample Consistencyeach allowed region overlaps with best fit point2-flavorCheck oscillation fit using different samples of data independently

Reconstruction of E and LFC single-ringEnEobservedEobserved EnNeutrino energy is reconstructed from observed energy using relations based on MC simulationZenith angle Flight lengthNeutrino flight length is estimated from zenith angle of particle directionNeutrino energyNeutrino directionPreliminaryL/E

Event samples in L/E analysis1.5m from top & bottom1m from barrel22.5kt26.4ktExpand fiducial volume More statistics for high energy muons Classify PC events using OD chargeOD stoppingOD through goingDifferent L/E resolutionFC single-ring, multi-ring m-likePCobserved charge / expectation from through-goingOD stoppingOD through-goingOD through-going MCOD stopping MCL/E

Sensitivities to alternative models n decayn decoherenceL/E resolution cut at 70%Assumptionnm nt2 flavor oscillation(Dm2=2.0x10-3eV2,sin22q=1.0)obtained Dc2Consistent with the expectation

Definition of c2Poisson with systematic errorsVarious systematic effects in detector, flux calculation and neutrino interaction are taken into accountNobs : observed number of eventsNexp : expectation from MCei : systematic error termsi: sigma of systematic errorL/E

Real Dm2 = positive assumed(No resonance for anti-neutrinos)En(GeV)cosQP(nmne)3-flavor

analytic calculation of Mij x ej = vi c2 definition for 3-flavor analysis

CC neCC neNC + OthersNC +OthersSingle-ring e-likeMulti-ring e-like3-flavor

SK-IIRebuilt in summer 2002Has 47% of original ID 20inch PMTs (~5200)20inch PMTs in acrylic shells to prevent future chain implosionsHas full OD 8inch PMTs (1885)Started data taking in Dec. 2002SK-II partially-contained sample

Number of Events(Event rate, Ev/day)Number of Events / Event rate in fiducial volumeSK2

SK-II149 daysSK-I1489 daysFully-containedevents1245(8.330.24)12180(8.180.07)Partially-containedevents80(0.540.06)911(0.620.02)