SK Atmospheric neutrino. Choji Saji ICRR,Univ. of Tokyo for the Super-Kamiokande collaboration

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1 SK Atmospheric neutrino Choji Saji ICRR,Univ. of Tokyo for the Super-Kamiokande collaboration

2 ontents Atmospheric neutrino oscillation using full Super-Kamiokande I(SK-I) data ν µ ν τ oscillation analysis CPT analysis Super-Kamiokande II(SK-II) current status

3 mospheric neutrinos Zenith angle dist. of Atmospheric ν flux He ±, K ± ν µ ν µ µ ± Downward L=10~100 km e ν e Zenith angle θ Upward L=up to km Flux(m -2 sec -1 sr -1 GeV -1 ) Eν > a few GeV Up/Down Symmetry

4 C Scientific American ν Event classification 42m Fully Contained (E ν ~1GeV) 39m ater Cherenkov detector Stopping µ (E ν ~10GeV) 000 m underground 0,000 ton (22,500 ton fid.) nner-detector(id): 11, inch PMTs(SK-I) uter-detector(od): 1,885 8 inch PMTs Partially Contained (E ν ~10GeV) Through-going µ (E ν ~100GeV)

5 Zenith angle distributions ν µ ν τ 2-flavor oscillations Best fit sin 2 2θ=1.0, m 2 =2.0x10-3 ev 2 Null oscillation Sub-GeV Multi-R µ-like Up stop µ Sub-GeV e-like Sub-GeV µ-like Multi-GeV µ-like + PC Multi-GeV Multi-R µ-like Up thru µ Multi-GeV e-like ~13000km ~500km ~15km ~13000km ~500km

6 Recent Improvements (after ν2002) MC improvements Three dimensional (3D) ν flux calculation ν interaction parameters Axial vector mass Fermi-momentum, nuclear potential Data analysis Ring selection, Particle ID, multi-ring fits Up-µ new automated precise fitter New calibs. and improved detector simulation

7 Flux Calculation Honda1D (Old) Honda3D (New) Fluka3D cosmic-ray proton flux used in Honda 2001 Honda 2001(3D) Absolute normalizati lower Enhancement in horizontal direction a low energies Not appear in observed zen angle distribution due to l scattering angle θ(ν µ)

8 ther improvements Neutrino interactions Axial vector mass(ma) was modified to agree with K2K near data Analysis tools Q.E. M A = Single π M A = Improved detector simulation Data reduction Fully automated FC and PC data reduction Event scanning for upward going muon analysis is greatly reduced (~100events/day 3events/day)

9 scillation Analysis Results (FC + PC + UP-µ) ν µ ν τ 2-flavor oscillations Preliminary Best fit: sin 2 2θ =1.0 m 2 = 2.0x10-3 ev 2 χ 2 = 170.8/170 dof 90% C.L. region: sin 2 2θ > < m 2 < 3.0x10-3 ev 2

10 ub-sample Consistency Check oscillation fit using different samples of data independently each allowed region overlaps with best fit point Preliminary

11 o finalize SK-I Results Re-estimation of systematic errors and improvements of the treatment of systematic errors Improvement of up-µ flux predictions analytical calculation full detector simulation

12 reatment of systematic errors in χ 2 calculation ld systematic errors These systematic errors are estimated as independent error terms But some error sources are multiply use (e.g. Eν spectrum index is used in δ, β1 β2, ρ, βl, βh) Each systematic error source is treated as independent error term

13 Neutrino flux flux absolute normalization flavor ratios(eν<1.33gev,eν>1.33gev) anti-neutrino/neutrino ratio(νe,νµ) Up/down ratio Horizontal-vertical ratio(3d calc., K/π) Neutrino flight length Energy spectrum Sample-by-sample normalization (FC multi-gev, PC+up stop µ ) Neutrino interaction A in quasi-elastic and single-pi uasi elastic scattering (model dependence) uasi elastic scattering (cross section) ingle-pion production (cross section) ulti-pion production (model dependence) ulti-pion production (cross section) oherent pion production (cross section) C/CC ratio uclear effect in 16 O harged current ν τ interactioin (C) Event selection a. FC reduction b. PC reduction c. Up-µ detection efficiency d. FC/PC relative normalization e. Hadron simulation f. Non-ν BG (e-like, µ-like) g. Through-going/stopping µ separation (D) Event reconstruction(6) a. 1-ring/multi-ring separation b. Particle ID (single-ring, multi-ring) c. Energy calibration for FC d. Energy cut for upward stopping µ e. Up-down asymmetry of energy calibration Total number of errors: 36 Treated as independent error term in χ2 calculation

14 Improvement of up-µ flux predictions Final SK-I result full paper (including νµ ντ oscillation analysis) is coming soon nalytical calculation ( Old ) ν C (New) ν µ fitter µ fitter θν = θµ θν = θµ smeared analytical calc. MC Upward stopping µ consider ν µ scattering angle Upward through-going µ

15 PT violation analysis( m 2 ν = m 2 ν) Up Stop µ P<400MeV/c µ-like P>400MeV/c µ-like Multi-GeV µ-like PC Multi-ring µ-like CPT conserving CPT violated ν (1.0,2x10-3 ev 2 ) ν (1.0,1.0eV 2 ) Up Through µ

16 CPT violation ( m 2 ν = m 2 ν) no CPT violation using 4 free parameters ( m 2, sin 2 2θ) for ν and ν Best fit : sin 2 (2θ) = 1.0 for ν and ν m 2 = 1.7x10-3 ev 2 for ν 2.1x10-3 ev 2 for ν 68, 90, 99% C.L. allowed region no evidence for CPT violation

17 SK-II

18 SK-II is taking data SK-II partiallycontained sample Rebuilt in summer inch PMT with Acrylic + FRP vessel Has 47% of original ID 20inch PMTs (~ inch PMTs in acrylic shells to prevent future chain implosions Has full OD 8inch PMTs (1885) Started data taking in Dec. 2002

19 tatus of SK-II Analysis 149 days of FC & PC data Now checking detector simulator and reconstruction tools Consistent event rate with SK-I Clear deficit in upward-going ν µ events Preliminary umber of events & Event rate (Preliminary) Multi-GeV FC µ-like +P Partiallycontained Fullycontained SK-II days 1245 ( ) 80 ( ) SK-I 1489 days ( ) 911 ( )

20 Summary -I analysis SK-I full data set (FC,PC 1489days, up-µ 1646 days) Improved data analysis and MC predictions ν µ ν τ allowed 90% C.L. 1.3 < m 2 < 3.0x10-3 ev 2, sin 2 2θ > 0.90 (Preliminary) SK-I final result will be published soon with updated systematic errors no evidence for CPT violation -II analysis is in progress Event rate is consistent with SK-I Deficit in upward going event in Multi-GeV µ-like + PC sample