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Takaaki Kajita, ICRR, Univ. of Tokyo

NOW2004, Sep 2004. SK Atmospheric Neutrino results and LBL experiments in Japan. Takaaki Kajita, ICRR, Univ. of Tokyo. Outline. SK Atmospheric neutrino results n m n t , L/E, and 3 flavor analysis K2K n m n t from K2K-I and -II T2K (Future long baseline experiment)

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Takaaki Kajita, ICRR, Univ. of Tokyo

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  1. NOW2004, Sep 2004 SK Atmospheric Neutrino results and LBL experiments in Japan Takaaki Kajita, ICRR, Univ. of Tokyo

  2. Outline • SK Atmospheric neutrino results nmnt, L/E, and 3 flavor analysis • K2K nmnt from K2K-I and -II • T2K(Future long baseline experiment) • Summary Only 2 and 3 flavor neutrino oscillations

  3. SK Atmospheric Neutrino results SK collaboration: Japan, USA, Korea, Poland

  4. Event classification and statistics Fully Contained (FC) (E ~1GeV)(12180) Partially Contained (PC)(E ~10GeV)(911) Stopping  (E~10GeV)(418) Red: observed number of events in SK-1 (total number = 15351) Through-going (E~100GeV)(1842)

  5. Recent improvements 1D • New n flux based on the 3 dimensional calculation • Tuned neutrino interaction MC based on the K2K data • 15  37 systematic error terms (S.Moriyama’s talk) 3D qnm(deg)

  6. Super-K atmospheric neutrino data CC ne CC nm 1489day FC+PC data + 1646day upward going muon data

  7. Binning for 2 flavor oscillation analysis Each box has 10 zenith bins Sub-GeV Multi-GeV Single-Ring m Multi-Ring m Up-stop Single-Ring e PC Up-through CC ne CC nm En 18 momentum bins x 10 zenith bins = 180 bins in total

  8. Neutrino oscillation parameters nm nt 90%C.L. c2=175.3/177dof @ Dm2=2.1x10-3,sin22q=1.00 (full paper will be published soon)

  9. m-like multi-GeV + PC SK collab. hep-ex/0404034 L/E analysis oscillation decoherence decay Should observe this dip! • Further evidence for oscillations • Strong constraint on oscillation parameters, especially Dm2

  10. FC single-ring m-like Full oscillation 1/2 oscillation D(L/E)=70% Selection criteria Select events with high L/E resolution (D(L/E) < 70%) Following events are not used: ★horizontally going events ★low energy events 2121 FC m-like and 605 PC Similar cut for: FC multi-ring m-like, OD stopping PC, and OD through-going PC

  11. 1489 days FC+PC L/E distribution MC (no osc.) Decoh. Decay Mostly down-going Mostly up-going Osc. • Evidence for oscillatory signature Decay and decoherence disfavored at 3.4 and 3.8s levels, respectively.

  12. Allowed neutrino oscillation parameters 1.9x10-3 < Dm232 < 3.0x10-3 eV2 0.90 < sin22q23(90% C.L.) c2min=37.9/40 d.o.f @ Dm2=2.4x10-3,sin22q=1.00 (sin22q=1.02, c2min=37.8/40 d.o.f)  Stronger constraint on Dm2  Consistent with that of the standard zenith angle analysis

  13. Matter effect cosQ En(GeV) Search for non-zero q13 (Dm122=0 assumed) MC, SK 20yrs 1+multi-ring, e-like, 2.5 - 5 GeV Electron appearance s213=0.05 s213=0.00 null oscillation cosQ Electron appearance in the 5 – 10GeV(En) upward going events.

  14. Super-K e-like data Multi-GeV, single-ring e-like Multi-GeV, multi-ring e-like (special) No evidence for excess of upward-going e-like events

  15. Binning for 3flavor analysis Same as 2 flavor analysis Different binning from 2 flavor Special in the 3 flavor ana. Sub-GeV Multi-GeV Up-stop Single-Ring m Multi-Ring m PC- stop Single-Ring e Multi-Ring e PC- through Up-through En CC ne CC nm 37 momentum bins x 10 zenith bins = 370 bins in total Fewer number of events per bin Poisson statistics to claculate c2

  16. prelim. n3 n2 n1 3 flavor analysis from Super-K sin2q13 Normal Dm2 sin2q23 sin2q13

  17. prelim. n2 n1 n3 3 flavor analysis from Super-K sin2q13 Inverted Dm2 sin2q13 sin2q23 No evidence for non-zero q13 (No information on the mass hierarchy)

  18. 10 1 P.Lipari NOON2004 Studies in progress…. Event rate = 1/kton/year Only upward going • Search for tau neutrino interactions • Oscillation analysis with the solar terms Statistical estimate of the nt interactions Simulated ntinteraction sub-GeV e-like events Peres, Smirnov NPB 680 (2004) 479 Also, M.Maltoni, this meeting, hep-ph/0408170

  19. SK-II atmospheric neutrino data Preliminary! SK-II event DATA Live time MC (no oscillation, normalized by live time) FC + PC 311.5 days Upward going m 243.5 days MC (oscillation, Dm2=2.1×10-3eV2, normalized by live time)

  20. 250km n K2K Collaboration K2K experiment JAPAN,KOREA, U.S.A., POLAND, CANADA, ITALY, FRANCE, SPAIN, SWITZERLAND, RUSSIA More details: K.Kaneyuki’s talk

  21. Far/Near Ratio beam MC w/ PION Monitor En (GeV) 1.0 2.0 K2K Analysis Overview KEK Near detectors #n, pm and qm F(En)near n int. MC 12GeV PS (8.9×1019 POT for Analysis) Far/Near Ratio F(En)far n int. MC SK Observation #n and En rec. Expectation #n and En rec. (sin22q, Dm2)

  22. Near detectors • 1KT Water Cherenkov Detector (1KT) • Scintillating-fiber/Water sandwich Detector (SciFi) • Scintillator Bar Detector (SciBar) after 2003 • Muon Range Detector (MRD) Muon range detector

  23. 1600 800 0 pm (MeV/c) Front detector measurements:m momentum and angular distributions NC Dis Coh p 1kton water Cherenkov 1kton water Cherenkov 1p QE 0 90 qm (deg.) Also, measurements by SciFi, SciBar and MRD detectors. Prediction of the number of events(150.9 +11.6-10.0) and spectrum at SK.

  24. GPS SK Tspill TSK TOF=0.83msec Event selection in Super-Kamiokande Decay electron cut 500msec Evis > 20MeV No activity in outer detector Event vertex in fiducial volume Evis > 30MeV 5msec 108 events obs’d Analysis time window 150.9 events exp’d TDIFF. (ms)

  25. Summary of K2K-SK events K2K I+II preliminary

  26. preliminary MC (no osc.) Number of events MC (osc.) Enrec[GeV] Deficit of events K2K energy spectrum (based on single-ring m-like events) MC normalization: number of events

  27. preliminary Best fit oscillation parameters • Best fit values. sin22q = 1.53 Dm2 = 2.1210-3 eV2 • Best fit values in the physical region. sin22q = 1.00 Dm2 = 2.7310-3 eV2 DlogL=0.64 Dm2 Toy MC 14.4% 2.73 sin22q=1.53 can occurr due to a a statistical fluctuation with 14.4% probability. 1.00 1.53 sin22q

  28. 90%CL preliminary Dm2[eV2] SK (L/E) K2K SK(zenith) sin22q Allowed parameter region Best fit values (in the physical region) sin22q = 1.00 Dm2 [eV2] = 2.710-3 Dm2=(1.7~3.5)×10-3 eV2 (90% C.L.) @ sin22q=1.0

  29. T2K experiment Super-Kamiokande JAERI T2K 250km J-PARC K2K Collaboration (at present): Canada, China, France, Italy, Japan, Korea, Poland, Russia, Spain, Switzerland, UK, USA

  30. T2K main physics goals 1st phase • Discovery of non-zero q13 • Precise measurement of sin22q23 and Dm232(Discovery of non maximal q23?) If q13≠0 observed 2nd phase • Discovery of non-zero CP phase

  31. 50GeV 50GeV dipole magnets Nuclear and Particle Experimental Facility Materials and Life Science Experimental Facility Nuclear Transmutation 3GeV Neutrino to Kamiokande 3 GeV Synchrotron (25 Hz, 1MW) 50 GeV Synchrotron (0.75 MW) Linac (350m) LINAC J-PARC = Japan Proton Accelerator Research Complex J-PARC Facility Under construction, expected completion (Phase-I)= end 2007

  32. OA0° OA2° OA2.5° OA3° T2K neutrino facility Off axis n beam facility To SK Near detectors (280m, and 2km(not approved yet)

  33. Measurement of Dm2 and sin22q23 Data sample: SK Monte Carlo, Fully-contained single-ring, muon-like events. π π Event fraction En from Em and qm Typical JHF neutrino energy Important to run the experiment with low energy beam.

  34. Reconstructed neutrino energy distribution ~ OA 2.5 deg. ~ No oscillation Dm2= 2.5 x10-3 eV2 Quasi Elastic non-QE reconstructed En (GeV) reconstructed En (GeV)

  35. Precise measurement of q23 , Dm223 normalization ( 5%) non-qe/qe ratio ( 5%) Assumed systematic errors E scale ( 1%) Spectrum shape (20%) Spectrum width ( 5%) d(Dm223) <1×10-4 eV2 d(sin22q23)~0.01 TrueDm232(10-3eV2) TrueDm232(10-3eV2)

  36. Present status: q13 Allowed sin2q13 Signal for non-zero q13 (nmne) BG (NC p0 ….)

  37. exp’d signal+BG total BG nm BG 50 Number of events 0 0 1 2 3 4 5 reconstructed En(GeV) Updated Measurement of nmne 10-1 Expected signal for DBG=10% CHOOZ limit 10-2 Dm2 (eV2) 10-3 10-4 10-3 10-2 10-1 1 sin22q13 More details: K.Kaneyuki’s talk

  38. T2K Phase-II ★0.77 → 4 MW beam power ★～1 Mton detector (Hyper-Kamiokande) 106 events (both nm and anti-nm) CP Violation

  39. Assumptions (not updated to the most recent solar parameters) Solid line: w/ matter Dashed line: w/o matter

  40. Expected CP violation signal (example) Neutrino run=2years, anti-neutrino run=6.8years, 4MW, 0.54Mton fid. Vol. sin22q13=0.1 Dm31<0 3s stat only 3s stat+2% syst. # of e+ events including BG 90%C.L. stat only 90%C.L. stat+2% syst. Dm31>0 CP phase # of e- events including BG

  41. 3s CP sensitivity CHOOZ excluded sin22q13<0.12@Dm312~3x10-3eV2 sin22q13 stat+5%syst. stat+2%syst. (signal+BG) stat only stat+10%syst. no BG signal stat only JHF-I: No indication for sin22θ13 sind 3s CP sensitivity : |d|>20o for sin22q13>0.01 with 2% syst.

  42. Neutrino facility construction Expected completion: early 2009 Beam Transfer line from 3GeV to Material and Life science Facility) OA2o OA3o Target Station ~15m Decay Volume ~110m Dump ~10m Construction started

  43. Summary • Present atmospheric neutrino data from SK are nicely explained by nm nt oscillations with; Dm2=1.9 – 3.0 × 10-3 eV2 sin22q > 0.90 (SK L/E analysis) • Recent L/E analysis has shown evidence for “oscillatory” signature. • No sub-dominant oscillation seen yet. • K2K has confirmed neutrino oscillations using the accelerator beam. • Neutrino oscillation results from K2K are in good agreement with the SK results. • T2K, a precision neutrino oscillation experiment, will start in 2009. • If non-zero q13 is observed in T2K phase-I, we would like to proceed to T2K phase-II to measure the CP phase.

  44. End

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