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Recent results on Atomospheric Neutrino Oscillation from Super-Kamiokande

Recent results on Atomospheric Neutrino Oscillation from Super-Kamiokande. Yoshihisa Obayashi Kamioka Observatory, ICRR, Univ. of Tokyo for the Super-Kamiokande Collaboration. 42 m. 39.3 m. Super-Kamiokande. 1996-. 2002 -. 2006 -. 2008 -. Mt. Ikenoyama (1396m) Kamioka , Japan.

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Recent results on Atomospheric Neutrino Oscillation from Super-Kamiokande

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  1. Recent results on Atomospheric Neutrino Oscillation from Super-Kamiokande Yoshihisa Obayashi Kamioka Observatory, ICRR, Univ. of Tokyo for the Super-Kamiokande Collaboration

  2. 42 m 39.3 m Super-Kamiokande 1996- 2002- 2006- 2008- Mt. Ikenoyama (1396m) Kamioka, Japan Acrylic (front) + FRP (back) 1000m(2700m.w.e.) Elec. Upgrade SK-I SK-II SK-III SK-IV SK Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK Imaging Water Cherenkov detector 50kt Pure Water 32kt Inner Detector viewed by20inch PMTs.Num of tubes:11146(SK-I), 5200(-II), 11129(-III,IV) t~2m Outer Detector viewed by1885 8inch PMTs

  3. proton Atmospheric Neutrino cosq=1(downgoing) L~15km cosq=0 p,K,… m cosq=-1(upgoing) L~13000km nm ne nm nm e ne nm/ne ~ 2 @En<a few GeV Zenith angle distribution ~Up/Down symmetric (In the case of NO oscillation) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  4. Event Topology FC PC UP-Stopmu UP-Thrumu Up-going Muons Energy spectrum of neutrino Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  5. Particle Identification Muon Decay Electron DATA MC(ALL)MC(nm CCQE) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK Identify Electron-like(Showering) particles and Muon-like particles using Cherenkov ring Pattern and Angle likelihood

  6. Zenith angle & lepton momentum distributions nm–ntoscillation (best fit) null oscillation SK-I+II+III momentum e-like m-like Preliminary Live time: SK-I 1489d (FCPC) 1646d (Upmu) SK-II 799d (FCPC) 827d (Upmu) SK-III 518d (FCPC) 636d (Upmu) Sub-GeV samples are divided to improve sensitivity to low-energy oscillation effects

  7. 2-flavor oscillation analysis results SK-I+II+III Preliminary Zenith Physical Region (1s) Dm232=2.11+0.11/-0.19 x10-3 sin22q23>0.96 (90%C.L.) L/E Physical Region (1s) Dm232=2.19+0.14/-0.13 x10-3 sin22q23>0.96 (90%C.L.) • Results of both zenith angle analysis and L/E analysis are consistent. • SK provides the most stringent limit for sin2(2θ23). Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  8. Full 3-flavor oscillation analysis • Consider both matter effectand solar term simultaneously. • Matter effect: possible enhancement of ne is expected in several GeV energy region and in Earth core • q13andmass hierarchycould be studied. • Solar term: possible enhancement of nein sub-GeV regionq23 octant degeneracycould be studied. • Interference: CP phasecould be studied. (when sin2q13 >~0.05). Difference in # of electron events: Matter effect Solar term Interference (The nm flux difference is also expected.) Interference Full 3-f osc. analysis: all parameters are considered simultaneously. PRD81, 092004: either matter effect or solar term is considered with approximations (cannot test the interference part) Solar term Matter Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  9. Full 3-flavor oscillation results SK-I+II+III Preliminary - Normal hierarchy - 0.4 .0035 .0035 99% C.L. 90% C.L. 68% C.L. best Excluded by CHOOZ at 90% C.L. .0015 .0015 0 - Inverted hierarchy - .0035 .0035 0.4 .0015 .0015 0 1 0.84 0 0.4 0 300 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  10. Full 3-flavor oscillation results - Normal hierarchy - SK-I+II+III Preliminary 2min = 469.94 /416dof - Inverted hierarchy - 2min = 468.34 /416dof • No significant preference on hierarchy. • No significant constraint on CP phase at 90% C.L. (sin2 12 , m212) are fixed at (0.304, 7.66x10-5 eV2) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  11. Comparison with 2-flavor analysis Full 3-flavor (90%) 99% C.L. 90% C.L. 68% C.L. best 2-flavor Full 3-flavor c2 -c2min distributions 99%C.L. 2-flavor (90%) 90%C.L. 68%C.L. Consistent results are obtained. No deviation of sin2q23 from 0.5. Allowed region of Dm223 is a bit larger than that of the 2-flavor analysis as the effect of CP phase is also taken into account. 90%C.L. allowed region (1dof, c2=c2min+2.71) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  12. Comparison of Hierarchies Multi-GeV samples tend to favor inverted hierarchy. Best fit is in the inverted hierarchy case Normal hierarchy (NH):2min= 469.94/416dof Inverted hierarchy (IH):2min= 468.34/416dof  ∆2 = 1.6 No significant difference • NH • IH There are also some contributions from Multi-GeV -like samples favoring IH to NH. Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  13. Search for CPT violation in atm. n SK-I+II+III Preliminary Neutrino: Dm232=2.2x10-3eV2 sin22q23=1.0 Anti-neutrino: Dm232=2.0x10-3eV2 sin22q23=1.0 No evidence for CPT violating oscillations is found Under the CPT theorem, P(n n) and P(n n) should be same. Test n oscillation or n oscillation separately. Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  14. Improvements of the DAQ system IEEE Trans. Nucl. Sci. 57 (2010) 428 SK-I,II,III: partial data above threshold (Num. of hits) were read (1.3msec window x3kHz) SK-IV: All hits above pulse height threshold are read, then apply complex triggers by software. Event build with variable time windows Precise analysis in parallel in real-time Periodic trigger (60kHz) New Electronics (QBEE) Clock Collect all hits every 17msec. PMT signals Readout (Ethernet) T2K GPS from J-PARC Typical event time windows: Super-Low-Energy (SLE) events (<~6.5MeV): -0.5/+1.0msec Normal events(>~6.5MeV): -5/+35msec Supernova Relic n (SRN) candidates(>~10MeV, No OD): -5/+535msec T2K events: -512/+512msec at T2K beam spill timing high rate (~3kHz) decay electrons neutrons Wider dynamic range for charge measurement of each channel (>2000pC) No dead time up to ~6MHz/10sec for Supernova burst neutrinos Apply precise event reconstruction to remove more low-e BG events in real-time x5 x100 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  15. Muon Decay Electron Tagging Parent muon t~2us Decay Electron SK-III (1.3us gate width) SK-IV (40us gate width) Expected decay curve Identified data Expected decay curve Identified data Wider gate width of SK-IV enables detectionof muon decay electronsat T~1us efficiently Detection Efficiency = 72.6% Detection Efficiency = 88.4% Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  16. Zenith angle distributions of SK-IV atm. n SK-IV e-like m-like Sub-GeV Sub-GeV nm–ntoscillation null oscillation SK-IV 449 days data Multi-GeV Multi-GeV PC StableData taking! Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  17. SUMMARY Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK • Recent update on Atmospheric neutrino oscillation from SK-I,II,III • 2 Flavor nm-nt oscillation result • Full 3 Flavor including Solar term & CP, Mass Hierarchy “Consistent with 2 flavor result, No preference of Hierarchy • CPT violations search  “No evidence” • Electronics Upgrade (SK-IV) • Improvement on Decay-electron tagging efficiency • Stable Atmospheric neutrino data taking • Super-Kamiokande Talk/Posters • M. Miura(Nucleon decay) 24-Jul-2010   09:20; BSM Session • H. Sekiya(Solar neutrino) Poster • M. Smy (Low-energy anti neutrino detection) Poster

  18. BACKUP SLIDES

  19. multi ring t nt decay-e nt appearance search Likelihood variables PRL97,171801 (2006) t-like selection; efft=43%, S/N=5% (Downward going) Data BKG MC Tau MC (a) Visible Energy (b) Max. decay-e distance from vertex (c) Ring Candidates (d) Sphericity in the lab frame (e) Clustered sphericity in COM frame Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  20. nt appearance search PRL97,171801 (2006) zenith angle distribution of tau enrich sample (Likelihood) tau enrich sample is consistent with nm-nt oscillation Best-fit tau excess: 138+/-48(stat.)+15/-32(syst.) Expected: 78+/-26(syst.) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

  21. History Kamiokande SK hall excavation(1994) Filling water (1996) “Evidence…”(1998) Accident(2001) SK-II starts soon(2002) SK-III starts soon(2006) Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK 1983 Kamiokande started observationto search for Proton decay 1987 Kamiokande observed SN1987a 1991 Construction of SK started 1996 SK started observation 1998 “Evidence for oscillation of atmospheric neutrinos” 1999 K2K started 2001 Accident 2002 Partial reconstruction SK-II started K2K-II started (-2004) 2006 Full reconstruction SK-III started 2008 Replacement of DAQ electronics SK-IV Started 2009 T2K started

  22. Kamioka Underground Site KamLAND (Tohoku Univ.) XMASS (Mar. 2008~) CANDLES (Mar. 2008~) Super-Kamiokande 40m Atotsu Entrance IPMU APIMS GC Ge det. Rn det. … (Mar.08~) Gadolinium project R&D (10mx15mx8~9mh, March 2010~) CLIO (Gravitational Wave) Laser extensometer (Geophysics) NEWAGE Superconductive gravimeter Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK

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