Neutrino Oscillations at Super-Kamiokande Soo-Bong Kim (Seoul National University) Super- Kamiokande C Scientific American 42m 39m Water Cherenkov detector 1000 m underground 50,000 ton (22,500 ton fid.) 11, inch PMTs 1,885 anti-counter PMTs SK-I: Apr 1996 Jul 2001 SK-II: Dec 2002 Completed recovery from Nov 2001 accident ! PMT coverage: SK-I 40% SK-II 20% Full recovery attempt will start from the fall of 2005. Super-Kamiokande is back to data-taking! (Dec. 10, 2002) SK-II cosmic ray muon sample Inner detector: ~5, inch PMT Outer detector: 1,885 8-inch PMT 20 inch PMT with Acrylic+FRP vessel SK-II Contents Results of atmospheric neutrino from SK-I: Re-analysis based on updated MC ( interaction model/ flux/detector simulation), event reduction and event reconstruction K2K results Results of solar neutrinos from SK-I: Detailed analysis on neutrino oscillations Any time modulation on the observed flux Neutrino Oscillation Two neutrino case () = ( cos sin - sin cos ) 1 2 () P( ) = sin 2 2 sin 2 (1.27 m 2 L/E) m 2 = m m 1 2 (eV 2 ) L (km): Distance from source to detector E (GeV): Neutrino energy Atmospheric Neutrinos , K ee e p, He... L=10-20 km ~10000 km Primary cosmic ray / e ~ 2 ( < a few GeV) flux is up-down symmetric (> a few GeV) Zenith Angle Distributions (old) 2-flavor oscillations 15km 13000km 500km 13000km 500km Best fit ( m 2 =2.5x10 -3 eV 2, sin 2 2 2 min =163.2/170 d.o.f) Null oscillation ( 2 =456.5/172 d.o.f) Updates in atmospheric analysis New neutrino flux (Honda 2001) Updated primary cosmic-proton flux 3D caculation Improved hadron interaction model Cosmic proton flux Updates in atmospheric analysis Improved neutrino interaction model: - changed M A Tuned SK detector simulation: - light scattering parameters in water - PMT gain parameters of outer detector Improved data reduction: - fully automated reduction scheme - lowered background of upward going sample Improved event reconstruction: - accurate ring search & automated reconstruction Zenith Angle Distributions (new) 2-flavor oscillations Best fit ( m 2 =2.0x10 -3 eV 2, sin 2 2 ) Null oscillation (Honda) oscillations ( m 23 2 ) Best fit( m 2 =2.0x10 -3,sin 2 2 =1.0 2 min =170.8/170 d.o.f) m 23 2 = (1.3~3.0)x10 -3 eV 2 sin 2 2 23 > 0.9 (90%CL) (Assuming null oscillation: 2 =445.2/172 d.o.f) (Complete SK-I data set) Allowed region for 3-flavor oscillations m 2 = m 23 2 m 13 2 ) getting close to CHOOZs limit on 13 e Atmospheric m 23 2 =2x10 -3 eV 2 Solar m 12 2 ~10 -5 eV 2 m1m1 m2m2 m3m3 K2K (KEK to Kamioka) Experiment Super-K Event selection (K2K-I) T spill T SK GPS T Spill : Abs. time of spill start T SK : Abs. time of SK event TOF: 0.83ms (KEK to Kamioka) No Decay-e HE Trig. FC: fully contained (No activity in Outer Detector) FV: 22.5kt Fiducial Volume 1.5 s 500 sec 5 sec T ( sec) FCFV 56 events ! Neutrino Interaction at Super-Kamiokande Best Normalized by area fit point no oscillation GeV Reconstructed E shape at SK 29 1-R events in Nov 99- Jul 01) w/ oscillations (KS-test = 79%) Result of Neutrino Oscillations from K2K-I (1.0, 2.8x10 -3 eV 2 ) K2K Best fit point = Null oscillation probability < 1% Method1 0.7% Method2 0.4% Method1 2.8x10 -3 Method2 2.7x10 -3 Super-K result Two independent methods agree with each other K2K-I Results Delivered Protons on Target (POT) POT Protons/spill (2003/10/20) 8.3 POT K2KI K2KII SciBar detector installed K2K Upgrade (SciBar Detector) Brand new near detector to study neutrino interactions below 1 GeV Scintillator + WLS fiber Scintillator: Fine segments (22300cm 3 ) (made by Fermi-Lab, MINOS type) WLS fiber (1.5mm x 360 cm) ~15,000 channels Solar Neutrinos (5/31/1996 ~ 7/15/2001, 1496 days) = Data SSM e e e e scattering (contains 15% of NC) solar events (14.5 events/day) Solar Signal Shape Solar Flux Time-Variatio n Background Shape Event Energy Event Time # Signal Events # Background Events in 21 bins 21 Energy bins Likelihood for solar neutrino extraction +1.3 A DN =-1.8 1.6 % -1.2 Perihelion (Jan. 4th) Aphelion (July 5th) Time Variation of Observed Solar Neutrino Fluxes at Super-Kamiokande Search for Periodic Modulation of Solar Neutrino Fluxes Lomb Periodogram Method