1. RECENT RESULTS IN K2K EXPERIMENT Shimpei YAMAMOTO (Kyoto Univ.) 10 th ICEPP Symposium @Hakuba 16-FEB-2004 Shimpei YAMAMOTO (Kyoto Univ.) 10 th ICEPP Symposium @Hakuba 16-FEB-2004

2. 10th ICEPP Symposium @Hakuba 2 JAPAN: High Energy Accelerator Research Organization (KEK) Institute for Cosmic Ray Research (ICRR), University 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 CANADA: TRIUMF / University of British Columbia EUROPE: Rome / Saclay / Barcelona / Valencia / Geneva RUSSIA: INR-Moscow K2K collaboration

3. 10th ICEPP Symposium @Hakuba 3 OutlineOutline K2K & neutrino oscillation Recent status & results –  → x oscillation analysis – e appearance –New near detector “SciBar” Prospects Summary K2K & neutrino oscillation Recent status & results –  → x oscillation analysis – e appearance –New near detector “SciBar” Prospects Summary

4. 10th ICEPP Symposium @Hakuba 4 K2K LBL oscillation exp. KEKSK 1kt SciFi MRD LG(K2K-I) SciBar(K2K-II)  Near Detectors =1.3GeV L=250km (fixed) 98%   Super-Kamiokande(SK) 50kt water cherenkov detector (22.5kt fid. vol.) 12GeV-PS@KEK beamline beamline Beam monitor

5. 10th ICEPP Symposium @Hakuba 5 Neutrino Oscillation in K2K oscillation prob.: Aiming results: –Reduction of events –Distortion of  spectrum – e appearance  osci. parameters (sin 2 2θ,Δm 2 ) –Near to far extrapolation –Rate & spectrum shape @SK null oscillation w/ oscillation

6. 10th ICEPP Symposium @Hakuba 6 Neutrino Beamline p+Al        +  e + + e (1.3%) +  (0.5%) double horm: high eff. of  collection Pion monitor: near/far flux ratio Muon monitor: beam intensity & direction Fast extraction every 2.2secFast extraction every 2.2sec Beam spill 1.1usBeam spill 1.1us

7. 10th ICEPP Symposium @Hakuba 7 Near Detectors (ND) fiducial fiducial 1kt Water Cherenkov detector (KT) 25 ton same type as SK Scintillation Fiber tracker (SciFi) 6 ton detect protons  QE/nQE Muon Range Detector (MRD) ~700 ton (Fe) beam monitor Lead Glass calorimeter (LG) detect electrons from SciFi K2K-I Mar,1999 – Jul,2001 Mar,1999 – Jul,2001 SKI (11146PMTs) SKI (11146PMTs) | SK accident SK accident |K2K-II Dec,2002 – Dec,2002 – SKII (~5200PMTs) SKII (~5200PMTs) LG removed LG removed SciBar (Oct,2003 -) SciBar (Oct,2003 -)

8. 10th ICEPP Symposium @Hakuba 8 Delivered protons on target 5~6x10 12 (protons per pulse) 10/7 12/21 6/23 12/23 ‘99 ‘00 ‘01‘02‘03 K2K-IIK2K-I 9.5x10 19 POT (8.4x10 19 for analysis)

9. 10th ICEPP Symposium @Hakuba 9 K2K event selection in SK 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 Expected atm. BG ~2x10 -3 within 1.5  s. 1.5  s  500  sec  5  sec FCFV 72 events Jun.’99 – Apr.’03 6.4 x 10 19 proton on target K2K-I + part of K2K-II

10. 10th ICEPP Symposium @Hakuba 10 K2K events in SK Jun.1999~Apr.2003 K2K-I (56 events) K2K-II (+16 events)

11.  → X oscillation analysis (K2K-I)  → X oscillation analysis (K2K-I)

12. 10th ICEPP Symposium @Hakuba 12 Analysis flow –N SK : Number of FCFV events –S SK (E rec ) : E rec distribution (shape) of 1R  Num. of events & Observed (p ,   ) distributionsNum. of events & Observed (p ,   ) distributions  Neutrino FluxNeutrino Flux Fit  spectrum & interaction modelFit  spectrum & interaction model – f near (E ) (8 bins) – nQE/QE ratio – Error matrix (to include correlation) Near to Far extrapolation: R FN (E ) Near site Prediction @far site Use Maximum Likelihood Fit in (sin 2 2 ,  m 2 )

13. 10th ICEPP Symposium @Hakuba 13 Reconstruction of E Reconstruction of E   proton  pp Use single-ring  -like FCFV (1R  ) eventsUse single-ring  -like FCFV (1R  ) events Assume QE int. and reconstruct EAssume QE int. and reconstruct E ( ~50% of K2K 1R  events are CCQE ) E rec. @SK:

14. 10th ICEPP Symposium @Hakuba 14 interaction (~1GeV) interaction (~1GeV) Charged current quasi-elastic scat, (CCQE) pion productions (nonQE) p  : muon momentum   : muon angle   proton  pp   nucleon  pp  ※ E can be reconstructed from P  and  . from P  and  . 1kt : single ring  -like FCFV SciFi: QE-like 2track single track (proton invisible) single track (proton invisible) 1kt : single/multi ring FCFV SciFi: nonQE-like 2track

15. 10th ICEPP Symposium @Hakuba 15 1KT : P  <1.5GeV/c, 4  acceptance – –1-ring  -like(1R  ) fully contained in Fid.25ton(FC) : 22,476ev. SciFi : P  >1GeV/c,   <60deg. – –1-track  -like : 5963ev. – –2-track QE-like (  p <25deg.) : 764ev. – –2-track nonQE-like (  p >30deg.) : 1288ev. PIMON – –  (p,  ) distribution ⇒ Neutrino Spectrum (>1GeV) Fitting Parameters E  : 8 bins, nonQE/QE ratio Spectrum measurement @ND nonQE-like QE-like

16. 10th ICEPP Symposium @Hakuba 16 SciFi p  /   1-track  2-track QE-like 2-track nQE-like  PP

17. 10th ICEPP Symposium @Hakuba 17 1kt p  /   p  and   distributions of 1kt 1ring  -like FCFV events PP 

18. 10th ICEPP Symposium @Hakuba 18 Allowed region (  → X ) Allowed region Use both Number of events + Spectrum shape (June ’99 – July ’01)(Nov. ’99 – July ’01) Null oscillation probability: less than 1%. Null oscillation probability: less than 1%.  m 2 =1.5~3.9 x 10-3 eV 2, sin 2 2  =1(90%CL)  m 2 =1.5~3.9 x 10-3 eV 2, sin 2 2  =1(90%CL) 68% 90% 99% 80.1 +6.2 -5.4 exp 56 obs ↔ Normalized by area reconstructed E Expectation w/o oscillation Best Fit Best fit point 2.8x10 -3

19. 10th ICEPP Symposium @Hakuba 19 Comparison w/ SK result 90% C.L. K2K SK

20. Search for e appearance (K2K-I)

21. 10th ICEPP Symposium @Hakuba 21 Search for e appearance Fully contained – Single ring – e-like (ring pattern and opening angle) (ring pattern and opening angle) Visible energy>100MeV – w/o decay electrons Ring pattern Opening angle To be submitted for publication data  MC NC of   MC e MC

22. 10th ICEPP Symposium @Hakuba 22 Data reduction summary DATA SETJune’99 – July’01 (4.8×10 19 POT) DATA SET: June’99 – July’01 (4.8×10 19 POT) DAT A  MCbeam e MCsignal e MC (CC) sin 2 2   e =1,  m 2 =2.8x10 -3 eV 2 8028 20 18 16 50 2.9 2.6 2.0 w/o decay-e 10.35 FCFV 560.82 Single ring 320.48 PID (e-like) 10.42 Evis>100Me V 10.41 NC:87% CC1  :7% CCm  4% CCQE:2% electron candidate: 1 event (obs.) 2.4 events (exp.) 2.4 events (exp.)

23. 10th ICEPP Symposium @Hakuba 23 Excluded region   → e ) sin 2 2   e  m 2 (eV 2 ) K2K(90%CL) CHOOZ(90%CL) e disappearance e disappearance SK atm. SK atm. allowed (90%CL)

24. Near Detector Upgrade

25. 10th ICEPP Symposium @Hakuba 25 SciBar detector Spec. & analysis status will be presented by following talkers.  Upgrade near detector to explore low E region (after removal of LG) Fine segmented scintillator trackerFine segmented scintillator tracker Scintillator target & fully activeScintillator target & fully active 2003.10.03~ Working well !!

26. 10th ICEPP Symposium @Hakuba 26 ProspectsProspects K2K-II is running stablyK2K-II is running stably ━ flux in low energy region by SciBar ━SciFI flux measurement using PID ━Improvement of Near/Far extrapolation (Harp) ━K2K events in SK-II New results of oscillation analysis come soon !

27. 10th ICEPP Symposium @Hakuba 27 SummarySummary K2K-I data has been analyzed so far:K2K-I data has been analyzed so far: –  → x oscillation analysis Null oscillation prob: less than 1% Null oscillation prob: less than 1%  m 2 =1.5~3.9 x 10 -3 eV 2 @sin 2 2  =1(90%CL) (consistent w/ atm. )  m 2 =1.5~3.9 x 10 -3 eV 2 @sin 2 2  =1(90%CL) (consistent w/ atm. ) – e appearance search 1 e candidate (consistent with BG) 1 e candidate (consistent with BG) K2K-II running stablyK2K-II running stably –New near detector SciBar –Low energy neutrino flux @ND –K2K events in SK-II –New results of oscillation analysis will come soon K2K-I data has been analyzed so far:K2K-I data has been analyzed so far: –  → x oscillation analysis Null oscillation prob: less than 1% Null oscillation prob: less than 1%  m 2 =1.5~3.9 x 10 -3 eV 2 @sin 2 2  =1(90%CL) (consistent w/ atm. )  m 2 =1.5~3.9 x 10 -3 eV 2 @sin 2 2  =1(90%CL) (consistent w/ atm. ) – e appearance search 1 e candidate (consistent with BG) 1 e candidate (consistent with BG) K2K-II running stablyK2K-II running stably –New near detector SciBar –Low energy neutrino flux @ND –K2K events in SK-II –New results of oscillation analysis will come soon

28. supplementssupplements

29. 10th ICEPP Symposium @Hakuba 29 Pion monitor Measure Momentum / Angle Dist. of π’s Just after Horn/Target +Well known π Decay Kinematics +Well Defined Decay Volume Geometry ⇒ Predict ν μ Energy Spectrum at Near Site Far Site ν μ Flux Ratio (Far/Near) as a Function of Neutrino Energy Ring Image Gas Cherenkov Detector (Index of Refraction is Changeable) To Avoid Severe Proton Beam Background, ν μ Energy Information above 1GeV is Available (β of 12GeV Proton ~ β of 2GeV π)

30. 10th ICEPP Symposium @Hakuba 30 Muon monitor Behind beam dump  sensitive to initially high energy  (>5.5GeV) Provide fast (spill-by-spill) monitoring of Intensity  targeting/horn stability Profile  beam direction Segmented Ionization Chamber Silicon Pad Detector Array

31. 10th ICEPP Symposium @Hakuba 31 Stability of spectrum @ND Neutrino spectrum measurement by the Pion monitor Energy and angle of muons produced in the CC interactions by MRD

32. 10th ICEPP Symposium @Hakuba 32 e candidate event e candidate event

33. 10th ICEPP Symposium @Hakuba 33 Method of flux fitting (ND)  2 =227 for 197 d.o.f. (90 from 1kt, 137 from FGD) for fitted (p    ) dist. of 1KT and FGD (124 data points) 0 ~0.5 GeV 0.5 ~0.75GeV 0.75 ~1.0GeV E QE(MC) non-QE(MC) neutrino spectrum  (E ) and interaction model (QE/non-QE ratio). Fit the parameters. Measured (p    ) 7bins 8bins pp  pp  Prepare MC templates  (E ), QE/non-QE ratio …

34. 10th ICEPP Symposium @Hakuba 34 Contribution of sys. errors on spectrum Total Spec.nQE/QESpec.+nQE/QE F/N  SK SK Escale