1. Status of T2K Tokai to Kamioka Neutrino Project at J-PARC June 21, 2004 Koichiro Nishikawa Kyoto University

2.  beam of ＜ 1GeV Kamioka J-PARC (Tokai-village)  → x  → x disappearance  → e  → e appearance NC measurement 0.75 MW 50 (40) GeV PS Super-K: 50 kton Water Cherenkov ~Mt “Hyper Kamiokande” 4MW 50GeV PS CP violation proton decay Approved exp (x10 2 of K2K) Future Extension “T2K” (Tokai-to-Kamioka) neutrino experiment LOI: hep-ex/0106019hep-ex/0106019 Collaboration Formed in May 2003 12 countries, 52 institutions 148 collaborators (w/o students)

3. Nuclear and Particle Experimental Facility Materials and Life Science Experimental Facility Neutrinos to Super-Kamiokande Linac (350m) 3 GeV Synchrotron (25 Hz, 1MW) Nuclear Transmutation J-PARC Facility 50 GeV Synchrotron (0.75 MW) J-PARC = Japan Proton Accelerator Research Complex

4. SuperKamiokande@Kamioka, Japan C Scientific American 42m 39m Water Cherenkov detector 1000 m underground 50,000 ton (22,500 ton fid.) 11,146 20 inch PMTs 1,885 anti-counter PMTs Since 1996. Accident on 2001. Partial recovery on 2002. (Full recovery on 2006)

5. The mixing angles  12,  23,  31,  ? –How small the mixing of 1 st and 3 rd generation? Does e contain  ? –Symmetry of 2 nd and 3 rd generation? How close  23 to  3 flavor analysis –Is sterile neutrino exist? Fraction in disappearance of  –How large is the phase  ? CP violation in lepton? Prepare for un-expected Neutrino beam –Suited for far detector technology water Cherenkov e   m1  m2  m3

6. Neutrino beam

7. Strategy High statistics by high intensity beam Tune E at oscillation maximum Sub-GeV beam –Low particle multiplicity suited for Water Cherenkov –Good E resolution : dominated by   n  p Narrow band beam to reduce BG 0.75MW 50GeV-PS Off-Axis beam Super-Kamiokande

8. Neutrino Interaction @~1 GeV & E reconstruction  CC QE  can reconstruct E    p    CC nQE  Bkg. for E measurement  NC  main Bkg. for electron appearance  + n →  + p -- p ( E , p  )   + n → + p +  ’s p  ’s --  + n →  + p +  p ( E , p  )   ’s

9. Neutrino cross section

10. E  reconstruction resolution  Large QE fraction for <1 GeV  Knowledge of QE cross sections  Beam with small high energy tail QE inelastic  E~60MeV <10% meaurement E  (reconstructed) – E  (true) 1-sin 2 2  non-QE resolution m2m2 + 10% bin High resolution : less sensitive to systematics

11. Off Axis Beam OA3° OA0° (ref.: BNL-E889 Proposal)  Target Horns Decay Pipe Super-K.  Quasi Monochromatic Beam  x 2~3 intense than NBB Statistics at SK (OAB 2 deg,1 yr,22.5 kt) ~ 4500  tot ~ 3000  CC e ~0.2% at  peak Tuned at oscillation maximum Neutrino energy spectrum  x  OA2° GeV

12. Extra handle on e contamination in the beam Off-Axis Beam ~1/500 from K e from  + K Intrinsic background: e /  (peak)  ~ 0.002

13. Primary physics goals

14. e appearance :   sin 2 2  13 Estimated background in Super-K Signal (~40% eff.) Signal + BG   NC    e beam  e total 0.112.010.71.70.524.9114.6139.5 0.0112.010.71.70.524.911.536.4 sin 2 2  13 m2m2 Off axis 2 deg, 5 years at sin 2 2  13 >0.006 CHOOZ excluded

15. Precision measurement of  23,  m 2 23 possible systematic errors and phase-1 stat. Systematic errors normalization (10% （  5%(K2K)) non-qe/qe ratio (20% (to be measured)) E scale (4% (K2K 3%)) Spectrum shape (Fluka/MARS →(Near D.)) Spectrum width (10%) OA2.5 o  (sin 2 2   )~0.01  (  m 2 23 ) <1×10 -4 eV 2

16. Neutrino facility

17. 50 GeV 0.75 MW beam ! cm 1100 o (cf. melting point 1536 o ) 3.3E14 ppp w/ 5  s pulse When this beam hits an iron block, Material heavier than iron would melt. Thermal shock stress (cf. stress limit ~300 MPa) Material heavier than Ti might be destroyed. Cooling power and radiation shield radio activity > 1000Sv/h

18. Jan.10, 2004 meeting from Director General of KEK In October CSTP rated the T2K project as C, the worst rating. We thought that CSTP's decision was completely wrong. So, we, KEK, struck back to get the better rating. Thanks to supports by many people, notably by M. Koshiba and some politicians, we were successful to have CSTP update the rating. Shocked by the rating, MEXT immediately established the review committee to judge if the T2K's should be funded next year, considering the scientific merit, urgency and collaboration's competence. The review report, which is attached here, was of course favorable and sent to CSTP. The committee chairman, Professor Kodaira, and MEXT's director general, Mr. Ishikawa, responded to CSTP members' questions. Finally S&T Minister Motegi agreed that the committee report was reasonable. He sent his comment to Ministry of Finance. After tough negotiations between MEXT and MOF backed by many and strong supports, MOF approved the T2K on December 20. （ as the first year of five-year construction project) - Now formally approved

19. However MOF approved only 6 oku-yen for proposed 8 oku-yen for FY 2004. You must work harder to be more cost effective. I want to urge you the following. CSTP will review the T2K and the whole J-PARC project every year. I suspect that the present manpower for the beam line construction is too weak and you will not be able to build it properly and timely. You should show us first of all how much you will improve the present situation. I urge the non-KEK collaborators NOT to be simple users of the beam line but to fully participate in the construction of the beam line. Otherwise I am afraid that T2K may eventually be terminated. Spokesperson should have sent this kind of statement long before. Best regards, Yoji Totsuka (KEK DG) Pion/Kaon production at 40-50 GeV ！

20. Muon monitors @ ~140m –spill-by-spill monitoring of  beam direction/intensity First Front detector @280m –0 degree definition –High stat. neutrino inter. studies (Second Front Detector @ ~2km for future addition) Far detector @ 295km –Super-Kamiokande (50kt) 1.5km 295km 0.28km Neutrino spectra at diff. dist dominant syst. in K2K p  140 m0 m280 m2 km295 km

21. Task force Identify the common project item and cost estimate for the contributions by next meeting from all countries to agree on (August) Write formal (technical) proposal by end of 2004.

22. decay pipe Near detector Target Station  -pit 280m 130m Neutrino facility in J-PARC (JFY2004-08) Special Features  Superconducting combined function magnets  Off-axis beam Funded components  Primary proton beam line Normal conducting magnets + INR Superconducting arc + BNL,Saclay Proton beam monitors + Canada  Target station + Canada  Target/Horn system + US  Decay pipe (130m Cover OA angle 2~3 deg. ) being constructed  Beam dump + UK  muon monitors + Canada, UK  Near neutrino detector

23. 20m  36m 33 22 SK direction 16m 5m FGD MRD ~14m SK Grid profile beam 3m 1m Concept of Near Neutrino Detector Off-axis (~2 o  0.2 0 ) –  and e neutrino fluxes and the spectra. – interaction study (CC-QE, non-QE,  0, ) – Kaon Contributions On-axis (0 o ) –Beam direction –Divergence –Beam stability The detector design is just started

24. Schedule Possible upgrade in future –4MW Super-J-PARC + Hyper-K ( 1Mt water Cherenkov) –CP violation in lepton sector –Proton Decay 20042005200620072008 MINOS OPERA/ICARUS 5yr (~20   SK full rebuild JHF- construction physics run K2K 2009

25. Sensitivity (3  ) to CP Violation Phase  with upgrades Preliminary Bkg. subtraction with 2% accuracy （ red), bkg(2%)+selection(2%) (black) errors Operation of 2 yr for  and 6.8 yr for   33deg at sin 2 2  13 =0.01  14deg for large sin 2 2  13 Understanding of background and systematics is essential Stat only

26. Summary The first “superbeam” long baseline neutrino exp. “T2K” approved –5 years construction (JFY2004~JFY2008) –Start physics in 2009 –Try to discover non-zero  13 –precision measurement of  23,  m 23 2. 1 st step to the CP violation in the Lepton sector International collaboration formed R&D in various components in the beam line and near detector Construction started

27. Construction status

28. December, 2003

29. Linac Area

30. 3 GeV Area

31. 31 3-50 GeV Area 3 GeV to 50 GeV

32. 32 50 GeV