Rencontres de Moriond (6 th March 2005) C. Mariani (INFN Rome) for K2K collaboration March 6 th, XLth Rencontres de Moriond

Rencontres de Moriond (6 th March 2005) K2K Collaboration 250km JAPAN: High Energy Accelerator Research Organization (KEK) / Institute for Cosmic Ray Research (ICRR), Univ. of Tokyo / Kobe University / Kyoto University / Niigata University / Okayama University / Tokyo University of Science / Tohoku University KOREA: Chonnam National University / Dongshin University / Korea University / Seoul National University U.S.A.: Boston University / University of California, Irvine / University of Hawaii, Manoa / Massachusetts Institute of Technology / State University of New York at Stony Brook / University of Washington at Seattle POLAND: Warsaw University / Solton Institute Since 2002 JAPAN: Hiroshima University / Osaka University U.S.A.: Duke University CANADA: TRIUMF / University of British Columbia ITALY: Rome FRANCE: Saclay SPAIN: Barcelona / Valencia SWITZERLAND: Geneva RUSSIA: INR-Moscow

Rencontres de Moriond (6 th March 2005)  1995 Proposed to study neutrino oscillation for atmospheric neutrinos anomaly.  1999 Started taking data.  2000 Detected smaller number of neutrinos than the expectation at a distance of 250 km. Disfavored null oscillation at the 2 level.  2002 Observed indications of neutrino oscillation. The probability of null oscillation is less than 1%.  2004 Confirm neutrino oscillation with both a deficit of  and the distortion of the E spectrum. Confirm neutrino oscillation with both a deficit of  and the distortion of the E spectrum. 1. Introduction and history of K2K

Rencontres de Moriond (6 th March 2005) 2. K2K experiment  monitor  monitor Near detectors (ND) ++  Target+Horn 200m decay pipe SK 100m ~250km  12GeV protons ~10 11   /2.2sec (/10m  10m) ~10 6   /2.2sec (/40m  40m) ~1 event/2days  Signal of oscillation at K2K Reduction of  events Distortion of  energy spectrum (monitor the beam center)

Rencontres de Moriond (6 th March 2005) Neutrino beam and the directional control ~1GeV neutrino beam by a dual horn system with 250kA. <1mrad The beam direction monitored by muons Y center X center ≤  1 mrad ~5 years

Rencontres de Moriond (6 th March 2005) Accumulated POT (Protons On Target) protons/pulse (×10 12 ) Accumulated POT (×10 18 ) K2K-I K2K-II 10.5x10 19 POT, 8.9×10 19 POT for Analysis Jan 03 Oct-Nov 04 K2K-I K2K-II

Rencontres de Moriond (6 th March 2005) Neutrino spectrum and the far/near ratio beam 250km Far/Near Ratio E  (GeV) beam MC w/ PION Monitor E (GeV)  energy K2K near detector

Rencontres de Moriond (6 th March 2005) SK Events (BG: 1.6 events within  500  s 2.4×10 -3 events in 1.5  s) T SK T spill GPS SK TOF=0.83msec 107 events Decay electron cut.  20MeV Deposited Energy No Activity in Outer Detector Event Vertex in Fiducial Volume More than 30MeV Deposited Energy Analysis Time Window  500  sec  5  sec T DIFF. (s)  T SK - T spill - TOF  1.3  sec

Rencontres de Moriond (6 th March 2005) 3. Analysis Overview Observation #, p  and   interaction MC Measurement  (E ), int. KEK Far/Near Ratio (beam MC with  mon.) Observation # and E  rec. Expectation # and E  rec. (sin 2 2 ,  m 2 ) SK

Rencontres de Moriond (6 th March 2005) NEUT: K2K Neutrino interaction MC  CC quasi elastic (CCQE)  CC (resonant) single (CC-1)  DIS  NC  /E ( cm 2 /GeV) E (GeV)

Rencontres de Moriond (6 th March 2005) 4. Near detector measurements  1KT Water Cherenkov Detector (1KT)  Scintillating-fiber/Water sandwich Detector (SciFi)  Lead Glass calorimeter (LG) before 2002  Scintillators Bar Detector (SciBar) after 2003  Muon Range Detector (MRD) Muon range detector LG calorimeter

Rencontres de Moriond (6 th March 2005) 4.1 1KT Flux measurement  The same detector technology as Super-K.  Sensitive to low energy neutrinos. Far/Near Ratio (by MC)~1×10 -6 M: Fiducial mass M SK =22,500Kton, M KT =25ton : efficiency  SK-I(II) =77.0(78.2)%,  KT =74.5% exp SK N =150.9 N = obs SK

Rencontres de Moriond (6 th March 2005) 4.2 SciBar neutrino interaction study  Full Active Fine-Grained detector (target: CH). Sensitive to a low momentum track. Identify CCQE events and other interactions (non-QE) separately.  p CCQE Candidate CCQE non-QE 25  p (degree)  p =  obs - CCQE  DATA CC QE CC 1  CC coherent-  CC multi-  2 track events p

Rencontres de Moriond (6 th March 2005) Neutrino energy reconstruction

Rencontres de Moriond (6 th March 2005) A hint of K2K forward  deficit. SciBar non-QE Events K2K observed forward  deficit. A source is non-QE events. For CC-1,  Suppression of ~q 2 /0.1[GeV 2 ] at q 2 <0.1[GeV 2 ] may exist. (0.1GeV 2 value comes from fitting 2 track nonQE sample in SciBar) For CC-coherent ,  The coherent may not exist. We do not identify which process causes the effect. The MC CC-1 (coherent ) model is corrected phenomenologically. Oscillation analysis is insensitive to the choice. q 2 rec (Data-MC)/MC DATA CC 1  CC coherent-  Preliminary q 2 rec (GeV/c) 2

Rencontres de Moriond (6 th March 2005) 4.3 Near Detector Spectrum Measurements  1KT Fully Contained 1 ring  (FC1R) sample.  SciBar 2 track nQE ( p >25  ) 1 track, 2 track QE ( p ≤25 ), 2 track nQE ( p >25  ) where one track is   SciFi 1 track, 2 track QE ( p ≤25 ), 2 track nQE ( p >30  ) where one track is  After applying the low q 2 suppression of nQE observed in SciBar, the angular distributions of all other samples are reasonably reproduced.

Rencontres de Moriond (6 th March 2005) 1KT:  momentum and angular distributions. with measured spectrum   (deg.) flux measurement low q 2 corr. p  (MeV/c) Kt -like sample Quasi elastic Single pion

Rencontres de Moriond (6 th March 2005) 4.4 Near Detectors combined measurements (p    ) for 1track, 2trackQE and 2track nQE samples  (E), nQE/QE  Fitting parameters (E ), nQE/QE ratio Detector uncertainties on the energy scale and the track counting efficiency. The change of track counting efficiency by nuclear effect uncertainties; proton re-scattering and  interactions in a nucleus …  Strategy  Measure (E ) in the more relevant region of   20 for 1KT and   10 for SciFi and SciBar.  Apply a low q 2 correction factor to the CC-1 model (or coherent ).  Measure nQE/QE ratio for the entire   range.

Rencontres de Moriond (6 th March 2005) GeV GeV GeV GeV E QE (MC) nQE(MC) MC templates KT data P  (MeV/c)  (MeV/c) flux  KEK (E ) (8 bins) interaction (nQE/QE)

Rencontres de Moriond (6 th March 2005) Flux measurements  2 =638.1 for 609 d.o.f  ( E< 500) = 0.78  0.36  ( 500 E < 750) = 1.01  0.09  ( 750 E <1000) = 1.12  0.07  (1000 E <1500) = 1.00  (1500 E <2000) = 0.90  0.04  (2000 E <2500) = 1.07  0.06  (2500 E <3000) = 1.33  0.17  (3000 E ) = 1.04  0.18 nQE/QE = 1.02  0.10 The nQE/QE error of 10% is assigned based on the sensitivity of the fitted nonQE/QE value by varying the fit criteria.  >10(20 ) cut: nQE/QE=0.95 0.04  standard(CC-1 low q 2 corr.): nQE/QE=1.02 0.03  No coherent: =nQE/QE=1.06 0.03 (E ) at KEK E preliminary

Rencontres de Moriond (6 th March 2005) SciFi (K2K-IIa with measured spectrum) P  1trk P  2trk QE P  2trk non-QE   1trk   2trk QE   2trk non-QE 02(GeV/c)040(degree) flux measurement 10

Rencontres de Moriond (6 th March 2005) SciBar (with measured flux) P  1trk P  2trk QE P  2trk nQE   1trk   2trk QE   2trk nQE flux measurement 10

Rencontres de Moriond (6 th March 2005) 5. Super-K oscillation analysis  Total Number of events  E rec spectrum shape of FC-1ring- events  Systematic error term f x : Systematic error parameters Normalization, Flux, and nQE/QE ratio are in f x Near Detector measurements, Pion Monitor constraint, beam MC estimation, and Super- K systematic uncertainties.

Rencontres de Moriond (6 th March 2005) K2K-SK events K2K-all (K2K-I, K2K-II) DATA (K2K-I, K2K-II) MC (K2K-I, K2K-II) FC 22.5kT 107 (55, 52) (79.1*, 71.8) 1ring 67 (33, 34) 93.7 (48.6, 45.1 ) -like 57 (30, 27) 84.8 (44.3, 40.5) e-like 10 (3, 7) 8.8 (4.3, 4.5) Multi Ring 40 (22, 18) 57.2 (30.5, 26.7) for E rec (56) * Updated from the previous analysis

Rencontres de Moriond (6 th March 2005) #SK Events Expected shape (No Oscillation) E rec [GeV] KS probability=0.08% V: Nuclear potential Toy MC CC-QE assumption

Rencontres de Moriond (6 th March 2005)  Best fit values. sin 2 21.51 m 2 [eV 2 ] = 2.1910 -3  Best fit values in the physical region. sin 2 21.00 m 2 [eV 2 ] = 2.7910 -3 logL= Results sin 2 2  =1.51 can occur due to a a statistical fluctuation with 12.6%. A toy MC sin 2 2 m2m %

Rencontres de Moriond (6 th March 2005)  N SK obs =107  N SK exp (best fit)=150.9 E rec [GeV] Best Fit KS prob.=36% m 2 [eV 2 ] sin 2 2 Data are consistent with the oscillation. Based on lnL preliminary

Rencontres de Moriond (6 th March 2005) Log Likelihood difference from the minimum.  m 2 <(1.87~3.58)×10 -3 eV 2 at sin 2 2=1.0 (90% C.L.) lnL - 68% - 90% - 99% - 68% - 90% - 99% m 2 [eV 2 ] sin 2 2

Rencontres de Moriond (6 th March 2005)  disappearance versus E shape distortion sin 2 2 m 2 [eV 2 ] N SK (#  ) E shape Both disappearance of  and the distortion of E spectrum have the consistent result.

Rencontres de Moriond (6 th March 2005) K2K-I vs K2K-II

Rencontres de Moriond (6 th March 2005) Null oscillation probability K2K-IK2K-IIK2K-all  disappearance 2.0%3.7%0.26% (3.0) E spectrum distortion 19.5%5.4%0.74% (2.6) Combined 1.3% * (2.5) 0.56% (2.8) % (4.0) K2K confirms neutrino oscillation discovered in Super-K atmospheric neutrinos. Disappearance of  and distortion of the energy spectrum as expected in neutrino oscillation. The null oscillation probabilities are calculated based on lnL. *: The value is changed from the previous one.

Rencontres de Moriond (6 th March 2005) 8. Summary has confirmed 4.0 (hep-ex/ )  With 8.910 19 POT, K2K has confirmed neutrino oscillations at 4.0 (hep-ex/ ). 3.0 Disappearance of  3.0 2.6 Distortion of E spectrum2.6 - 68% - 90% - 99% K2K new results preliminary m 2 [eV 2 ] sin 2 2

Rencontres de Moriond (6 th March 2005) Backup slide

Rencontres de Moriond (6 th March 2005) Additional Error on nonQE  nonQE value depends on fitting condition. Small angle cut: CC1 re-weighting: No coherent : CC1 re-weighting factor +/ – 0.03 (1) (SciBar only fit): +/ – 4%  In total, ~10% uncertainty exists. Fitting error is ~5%  add 10% to nonQE error. Official value 8% 3.5%

Rencontres de Moriond (6 th March 2005) 7. Other Physics in K2K (K2K-I data only) M  (MeV)  +H 2 ONC1 0 sin 2 2 e m 2 [eV 2 ] 90%CL limit 90%CL sensitivity   e search PRL 93 (2004) =0.064 (our MC) =0.065 0.0010.007 not NC1 0 1KT

Rencontres de Moriond (6 th March 2005) NEUT: K2K Neutrino interaction MC  CC quasi elastic (CCQE) Smith and Moniz with M A =1.1GeV  CC (resonance) single (CC-1) Rein and Sehgal ’ s with M A =1.1GeV  DIS GRV94 + JETSET with Bodek and Yang correction.  CC coherent  Rein&Sehgal with the cross section rescale by J. Marteau  NC + Nuclear Effects  /E ( cm 2 /GeV) E (GeV)

Rencontres de Moriond (6 th March 2005) Overall normalization error on Nsk for Nov99~ (Event) Stat % KT % SK % Flux F/N NC/CC nQE/QE CT % Total Central Value 76.05evts Take errors not considered in matrix 5.34% KT: dominated by FV error SK: also. Errors

Rencontres de Moriond (6 th March 2005) Null oscillation  lnL K2K-IK2K-IIK2K-all  disappearance E spectrum distortion Combined K2K confirmed neutrino oscillation discovered in Super-K atmospheric neutrinos. Disappearance of  and distortion of the energy spectrum as expected in neutrino oscillation. The null oscillation probabilities are calculated based on lnL. preliminary *: The value is changed from the previous one.

Rencontres de Moriond (6 th March 2005) The change of N SK exp in K2K-I (Bugs)  The detector position 295m  294m -1%  MC difference between KT and SK KT; M A (QE)=1.1 (NC el ) KT =1.1×(NC el ) SK SK; M A (QE)=1.0  Efficiency change! -1% N SK exp Change ~2% 295m 294m

Rencontres de Moriond (6 th March 2005) CC-1  suppression versus coherent 

Rencontres de Moriond (6 th March 2005) Systematic Bias without the MC correction. Oscillation Results ND (SciBar) measurement DATA; MC w/ CC-1  suppression MC template; Default MC systematic bias flux nQE/QE Toy MC MC w/o low q 2 correction sin 2 2  =1.00  m 2 =2.65 ×10 -3 eV 2 Prob.(null oscillation)=0.0049% Corrected MC for low q 2 sin 2 2  =1.00  m 2 =2.73×10 -3 eV 2 Prob.(null oscillation)=0.011% There is a small bias in nQE/QE and the low energy flux.

Rencontres de Moriond (6 th March 2005) Oscillation result with a default MC Without low q 2 MC correction The result w/o low q 2 MC correction gives the better (biased) measurement due to the more low energy flux and the smaller nQE/QE.

Rencontres de Moriond (6 th March 2005) K2K-I vs K2K-II  Best fit values. sin 2 21.08, 1.51 m 2 [eV 2 ] = 2.7310 -3, 2.1910 -3  Best fit values in the physical region. sin 2 21.00, 1.00 m 2 [eV 2 ] = 2.8610 -3, 2.7910 -3 logL=0.02, 0.75 KS K2K-I & K2K-II =77%

Rencontres de Moriond (6 th March 2005) E rec for K2K-I and K2K-II K2K-I K2K-II

Rencontres de Moriond (6 th March 2005) K2K-I vs K2K-II

Rencontres de Moriond (6 th March 2005)  1KT sys error summary and the change.  SciBar sys. error  …

Rencontres de Moriond (6 th March 2005) Systematic error Fiducial: updated +-4.0% (<- 4.0%) : Smy ’ s analysis Escale : updated +-0.3% FADC (scale) updated +-0.8% FADC(cut position) +-1.5% (New) : Shaomin ’ s analysis Background +-0.5% Multi-event +-0.7% Event rate(New) +-2.0% Profile (New) +-0.3% KT origin +-4.9% (Prev. 4.4%) SK efficiency +-3.0% CT norm % for K2K-II ±0.6% for K2K-I Far/Near % 1KT sys. error

Rencontres de Moriond (6 th March 2005) SciBar Systematic Error (2track/1track) Detector oriented  Vertex Matching Efficiency +2.7% -1.0%  Threshold Effect (+-15%) +0.7%  Xtalk Effect (2%/4%/6%) +1.1% -1.1%  Finding Efficiency +0.9% -4.3%  Total (Detector) +3.1% -4.5% Nuclear Effect  Proton Re-scattering +2.9% -2.6%  Pion Absorption +1.7% -1.7%  Pion inelastic scattering +2.3% -2.9%  Total (Nuclear) +4.1% -4.2% Total +5.1% -6.2%

Rencontres de Moriond (6 th March 2005) Detector oriented  Angle resolution +1.0%  X-talk Effect +2.2% -2.9%  Momentum scale (+-2.7%) +1.5% -4.3%  Total (Detector) +2.8% -5.2% Nuclear Effect  Proton Re-scattering +2.9% -2.8%  Pion Absorption -5.4%  Pion inelastic scattering +0.3% -4.7%  Total (Nuclear Effect) +2.9% -7.7% Total +4.0% -9.3% SciBar Systematic Error (2track QE/2track nQE)

Rencontres de Moriond (6 th March 2005) Track finding Efficiency 2nd Track Efficiency (MC) MC true 2 nd Track (NHITX/Y ≧ 3Hit) Detected! (= 1. Could Find 2 nd Track 2. Rec.track overlap with more than 1 true Hit) Overall Eff. 59.0% >20Hit 85.3% >40Hit 91.1% (This can be improved!) Evaluated DATA/MC w/ Eye scan (NHIT) Finding Efficiency

Rencontres de Moriond (6 th March 2005) Eye scan Result ● Data (Eye) □ MC (Eye) Integrated bin (>40Hits) Eye scanners (M.Hasegawa,K.Hiraide Y.Takubo,S.Yamamoto)

Rencontres de Moriond (6 th March 2005) Entry < – (each bin MC) DATA/ MC (stat.err) Total track/1track : (27418/54106)  / (27034/54490) Systematic Error (Track finding Eff.) : + 0.9%, -4.3% Systematic error (Finding Eff.) 2Track/1Track (default MC) vs 2Track/1Track (MC* ) DATA MC Compared

Rencontres de Moriond (6 th March 2005) Same as previous one except binning size is 125/2 nsec that is a half of intervals of two bunches.

Rencontres de Moriond (6 th March 2005) Residual of K2K-SK event timing relative to neutrino beam bunches. Timing correlation is clearly seen and a sigma is obtained as about 30nsec.

Rencontres de Moriond (6 th March 2005) Number of observed events (F.C. in fid. vol.) as a function of integrated CT

Rencontres de Moriond (6 th March 2005) Number of observed events (F.C. in all inner volume) as a function of integrated CT

Rencontres de Moriond (6 th March 2005) Results (without small angle)  1kt  > 20deg., SciFi and SciBar  > 10deg.  In each E bin, fitted flux is consistent each other.

Rencontres de Moriond (6 th March 2005) A A=0.10 +/– 0.03  CC1  q 2 /0.10 (Data–MC)/MC Agree quite well  By using SciBar 2track- nonQE and fitted flux, I looked for the best value of CC1 suppression.  Suppression factor q 2 /A (q 2 >A)  Scan A value and calculate  2 of  distribution. Calculate  2 SciBar 2track nonQE CC1  suppression factor tuning

Rencontres de Moriond (6 th March 2005) Results (CC1  re-weighted)  CC1 re-weighting factor : q 2 /0.10 (q 2 <0.10)  Flux is fixed  nonQE value : 0.979( cut)  1.056(this result) (+8%)

Rencontres de Moriond (6 th March 2005) Results (no coherent  ) for comparison  Coherent  production removed.  Flux is fixed.  nonQE value: 1.093(this results)  (CC1 re-weighting : % difference)

Rencontres de Moriond (6 th March 2005) Results (no cut, no re-weighting) for comparison  Flux is consistent with  cut results.  nonQE is significantly small, and  2 is bad.  nonQE : 0.856,  2 / dof = / 595 = 1.30

Rencontres de Moriond (6 th March 2005) Flux v.s. fitting condition Official flux For comparison  Fitted flux from  cut, CC1 re-weighting and no coherent are consistent each other.

Rencontres de Moriond (6 th March 2005) NonQE v.s. CC1  re-weighting factor (SciBar only fit)  CC1 re-weighting factor +/ – 0.03 (1)  nonQE +/ – 4% SciBar Only Fit

Rencontres de Moriond (6 th March 2005) Likelihood for Oscillation analysis Poisson prob. for FC events : # of observed events : # of expected events Period flux SK parameters K2K-Ia I horn = 200 kA SK-I K2K-Ib I horn = 250 kA K2K-II SK-II f x : Systematic error parameters

Rencontres de Moriond (6 th March 2005) Likelihood for Normalization i: energy bin j: Interaction mode Data/MC for # of events in KT flux Far/Near # of interaction in MC SK efficiency nQE/QE

Rencontres de Moriond (6 th March 2005) Likelihood for Spectrum Shape N: Normalization factor N j (E rec,E true ): Event fraction in MC flux Far/NearnQE/QE SK efficiency SK Energy Scale

Rencontres de Moriond (6 th March 2005) Likelihood for Systematic parameters Overall Normalization SK Energy Scale neutrino flux, nQE/QE,NC Far/Near Ratio SK efficiency Systematic parameters for flux are common for SK-Ib and SK-II # of free parameter in fit: 25  (f nQE  f CC-nQE, f NC )

Rencontres de Moriond (6 th March 2005) K2K-1K2K-2 Reconstructed vertex distribution for r 2 vs Z

Rencontres de Moriond (6 th March 2005) Visible energy distribution for F.C. events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Visible energy distribution for F.C. events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Visible energy distribution for F.C. events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Reconstructed muon momentum distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0× eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0× eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Reconstructed muon momentum distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0× eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0× eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Reconstructed muon momentum distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0× eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0× eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) The distribution of the reconstructed direction of muons relative to the direction from KEK to SK for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) The distribution of the reconstructed direction of muons relative to the direction from KEK to SK for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) The distribution of the reconstructed direction of muons relative to the direction from KEK to SK for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Reconstructed neutrino energy distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Reconstructed neutrino energy distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram)

Rencontres de Moriond (6 th March 2005) Reconstructed neutrino energy distribution for F.C. 1ring mu-like events in the fiducial volume in data (closed circle), M.C. expectation with no oscillation (solid histogram), oscillated with sin 2 2  =1.0,  m 2 =2.0×10 -3 eV 2 (dashed histogram), and oscillated with sin 2 2  =1.0,  m 2 =3.0×10 -3 eV 2 (dotted histogram).

Rencontres de Moriond (6 th March 2005) Summary of SK-2 absolute energy calibration Data agree with MC within +/-1.9% Time variation : +/-0.9% total uncertainty : +/- 2.1%

Rencontres de Moriond (6 th March 2005) Ring-counting likelihood for SK-2  -like events sub-GeV P<400MeV/csub-GeV P>400MeV/c multi-GeV

Rencontres de Moriond (6 th March 2005) PID distributions for SK-2 sub-GeV (Evis<1330MeV) multi-GeV (Evis>1330MeV)

Rencontres de Moriond (6 th March 2005) Systematic error on spectrum K2K-1 ring counting PID vertex E scale % 1.1% 2.0% % 0.5% 2.0% % 0.7% 2.0% % 0.6% 2.0% % 0.7% 2.0% % 0.7% 2.0% 2.7% K2K-2 ring counting PID vertex E scale % 2.5% 2.0% % 0.9% 2.0% % 0.6% 2.0% % 0.5% 2.0% % 0.5% 2.0% % 0.5% 2.0% 2.1%