1 The JHF-Kamioka Neutrino experiment 1.Introduction 2.Overview of the experiment 3.Physics sensitivity in Phase-I 4.Physics sensitivity in Phase-II 5.Summary and Conclusion Tsuyoshi NAKAYA (Kyoto U.) for JHF-SK working group Jan 16, JHF is an tentative name, and will be renamed soon.

2 JHF-SK Neutrino Working Group ICRR/Tokyo-KEK-Kobe-Kyoto-Tohoku-TRIUMF 15,5 Y. Itow, T. Kajita, K. Kaneyuki, M. Shiozawa, Y. Totsuka (ICRR/Tokyo) Y. Hayato, T. Ishida, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Obayashi, M. Sakuda (KEK) S. Aoki, T.Hara, A. Suzuki (Kobe) A. Ichikawa, T. Nakaya, K. Nishikawa (Kyoto) T. Hasegawa, K. Ishihara, A. Suzuki (Tohoku) A.Konaka (TRIUMF, CANADA) In addition to the above user group, the neutrino facility construction group is OFFICIALLY formed at KEK.

3 1.Introduction ~1GeV beam Kamioka JAERI (Tokaimura) 0.77MW 50 GeV PS ( conventional beam) Super-K: 22.5 kt 4MW 50 GeV PS Hyper-K: 1000 kt Phase-I (0.77MW + Super-K) Phase-II (4MW+Hyper-K) ~ Phase-I  200 The experiment will start in 2007.

4 Lepton Sector Mixing  12,  23,  13 +   m 2 12,  m 2 23 MNS (Maki-Nakagawa-Sakata) matrix

5 oscillation at  23 ~  /4 and  13 ~0

6 Targets of JHF-SK experiment Confirmation of    Discovery of   e  at  m 2 atm. Precise measurement of neutrino oscillation. (observation of oscillation peak) CP violation in neutrino oscillation. Confirm or Reject LSND anomaly.

7 2. Overview of the experiment Construction 2001 ～ 2006 (approved) JHFMINOSK2K E(GeV) Int.(10 12 ppp ) Rate(Hz) Power(MW ) (60km N.E. of KEK) Super Conducting magnet for beam line Near POT(130day)≡ “1 year”

8 beam at JHF Principle –Intense Narrow Band Beam –Beam energy is tuned to be at the oscillation maximum. High sensitivity Less background –~1 GeV beam energy for Quasi-elastic interaction. E (reconstruct) – E (True) (MeV)  m 2 =1.6~4x10 -3 eV 2 E =0.4~1.0GeV  =80MeV  + n →  + p  p ( E , p  )

9 Off Axis Beam WBB w/ intentionally misaligned beam line from det. axis (ref.: BNL-E889 Proposal)  Target Horns Decay Pipe Far Det. ～ 3100 int./22.5kt/yr w/ 80m long decay volume e : 1.0% peak) Decay Kinematics ~2° E (Present design; 130m  40% more  )

10 detectors at JHF 1 Mton (fiducial) volume: Total Length 400m (8 Compartments) Super-K 40m Total Length 400m (8 Compartments) Phase-I: Suker-K 22.5kt (50kt) Phase-II: Hyper-K 1Mton (fiducial) volume: We are investigating the possible site at Kamioka. 70m

11 Near Detectors ( Detectors at two locations are (1~10 events/spill/100ton) Fine Grained w/ magnet. –Measure direction and spectrum. –Measure wrong sign component (see CP section). –Will be used for interaction study with NBB. –Non-oscillation (0.1 events/spill/100ton) Water Cherenkov + Fine Grained –Measure spectrum and e background since they are same as those at Kamioka. –Test LSND anomaly if Mini-Boone failed to test it or discovered the new physics.

12 Far/Near Spectrum Ratio spectrum 0.28km 1.5km 295km At >1.5km, the source is treated as a point source  Low Ep High Ep

13 3. Physics sensitivity in Phase-I (w/ Super-K) 5years (5  POT) running  precise measurement of  m  2   23 and  13    (  m  2   23 )   e (  13, open window for CP study)    w/ NC interactions. (confirmation) stringent limit on the non-oscillation scenario and the existence of s. Sensitivity (goal):  sin 2 2    sin 2 2    CL   m  2    eV 2 at  sin 2 2  m 2    eV 2 

14   →  confirmation w/ NC interaction NC  0 interaction ( + N → + N +  0 )    e CC + NC(~0.5CC) ~0 (sin 2 2   e ~0)  CC + NC(~0.5CC) ~0 (maximum oscillation)   NC #  0 is sensitive to  flux. Limit on s (  f( s)~0.1 ) OAB      s  =390±44 #  0 + #e-like  m       CC NC

15  e appearance  C.C.  N.C.Beam e Osc’d e Generated ring e-like red. eff.0.1%6.1%23.4%67.5% e/  0 sep red.eff.0.03%0.6%7.5%50.4%.4<E < red.eff.0.02%0.2%3.8%40.8% e 00

16 e appearance Background rejection against NC  0 is improved. sin 2 2   e =0.05 (sin 2 2   e  0.5sin 2 2  13 ) 3×10 -3 ×20 improvement CHOOZ sin 2 2   e m2m2

17  disappearance 1ring FC  -like Reconstructed E (MeV) Oscillation with  m 2 =3×10 -3 sin 2 2  =1.0 No oscillation Non-QE (linear) (log)  m 2 =3×10 -3 sin 2 2  =1.0 ~3% Ratio after BG subtraction m2m2 sin 2 2   sin 2 2     m  2    eV 2 Fit with 1-sin 2 2  ・ sin 2 (1.27  m 2 L/E)

18 4. Physics sensitivity in Phase-II (w/ Hyper-K) 2 years ( 10  POT ) for  and 6 years ( 30  POT ) for  running  Search for CP violation in oscillation. standard:   e vs   e non-standard:    vs    w/ NC  Search for   e  Search for proton decays. Sensitivity (goal): sin 2 2      CL     discovery  at  m 12 2    eV 2  m 23 2    eV 2   proton B(p  e  0, K) > years

19 CP violation in oscillation L=295km : small matter effect E ~1 GeV : large CP asymmetry  A cp

20    flux for CP violation search.   POT/yr (1st phase) Sign flip by change of horn plarity Flux CC interaction   Wrong sign BG cross section difference

21 CP Violation Study Compare   e with   e N(e - ) N(e + ) NO CP violation w/o matter effect.  m 12 2    eV 2   m 23 2    eV 2 sin 2 2          discovery 

22 5. Summary and Conclusion The experiment is expected to start in 2007 at the same time of the completion of JHF 50 GeV PS. –The experiment is not approved yet, and we need your STRONG support to put the experiment on track. The features of the experiment are: –MW class 50 GeV proton accelerator (0.77MW  4MW) –~1GeV Narrow band neutrino beam at the oscillation maximum (L=295km). –Gigantic Water Cherenkov detectors with/ neutrino energy reconstruction by quasi-elastic interaction. (22.5kton  1000kton)

23 Physics Reach (see hep-ex/ ) Phase-I (0.77MW kt): NC interaction:  Establish    and limit on   s    :  sin 2 2      e : sin 2 2    CL     :  m  2    eV 2 at  sin 2 2  m 2    eV 2  Phase-II (4MW kt):   e : sin 2 2      CL    e vs   e :    discovery  at  m 12 2    eV 2  m 23 2    eV 2   proton B(p  e  0, K) > years