Status of T2K Tokai to Kamioka Neutrino Project at J-PARC

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

2. “T2K” (Tokai-to-Kamioka) neutrino experiment LOI: hep-ex/0106019 nmbeam of ＜1GeV Kamioka Super-K: 50 kton Water Cherenkov J-PARC (Tokai-village) 0.75 MW 50 (40) GeV PS ~Mt “Hyper Kamiokande” 4MW 50GeV PS Approved exp(x102 of K2K) • nm→ nxdisappearance • nm→ neappearance • NCmeasurement • Collaboration • Formed in May 2003 • 12 countries, 52 institutions • 148 collaborators (w/o students) Future Extension • CPviolation • proton decay

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

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

5. The mixing angles q12, q23, q31, d? • How small the mixing of 1st and 3rd generation? • Does ne contain n3? • Symmetry of 2nd and 3rd generation? • How close q23 to p/4?3 flavor analysis • Is sterile neutrino exist? • Fraction in disappearance of nm • How large is the phase d? • CP violation in lepton? • Prepare for un-expected • Neutrino beam • Suited for far detector technology • water Cherenkov ne nm nt nm1nm2nm3

6. Neutrino beam

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

8. m- nm+ n→ m+ p (Em, pm) qm n p m- nm+ n→ m+ p+ p (Em, pm) qm n p p’s n nm+ n→ n+ p+ p’s n p p’s Neutrino Interaction @~1 GeV & En reconstruction • CC QE • can reconstruct En (qm,pm) • CC nQE • Bkg. for En measurement • NC • main Bkg. for electron appearance

9. Neutrino cross section

10. non-QE resolution 1-sin22q Dm2 En reconstruction resolution • Large QE fraction for <1 GeV • Knowledge of QE cross sections • Beam with small high energy tail dE~60MeV <10% meaurement QE inelastic En (reconstructed) – En (true) + 10% bin High resolution : less sensitive to systematics

11. Super-K. q Decay Pipe Target Horns Off Axis Beam (ref.: BNL-E889 Proposal) • Quasi Monochromatic Beam • x 2~3 intense than NBB Tuned at oscillation maximum Neutrino energy spectrum sxF OA0° OA2° Statistics at SK (OAB 2 deg,1 yr,22.5 kt) ~ 4500nmtot ~ 3000nmCC ne~0.2% atnmpeak OA3° GeV

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

13. Primary physics goals

14. ne appearance : q13 at Off axis 2 deg, 5 years CHOOZ excluded Dm2 Off axis 2 deg, 5 years sin22q13>0.006 sin22q13

15. Precision measurement of q23 , Dm223possible 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%) OA2.5o d(sin22q23)~0.01 d(Dm223) <1×10-4 eV2

16. Neutrino facility

17. 50 GeV 0.75 MW beam ! radio activity > 1000Sv/h 3.3E14 ppp w/ 5ms pulse When this beam hits an iron block, cm 1100o (cf. melting point 1536o) • 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

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 usersof 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. Neutrino spectra at diff. dist 1.5km 295km 0.28km p p n • Muon monitors @ ~140m • spill-by-spill monitoring of p-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) 0 m 140 m 280 m 2 km 295 km dominant syst. in K2K

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. 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 Neutrino facility in J-PARC (JFY2004-08) Proton beam transport Target Station 130m decay pipe 280m m-pit Near detector

23. Off-axis (~2o0.20) nm and ne neutrino fluxes and the spectra. n interaction study (CC-QE, non-QE, p0, ) Kaon Contributions On-axis (0o) Beam direction Divergence Beam stability The detector design is just started Concept of Near Neutrino Detector 16m SK SK direction FGD Grid n profile MRD 36m 2 1m n beam 5m 3 ~14m 1m 3m 20mF

24. Schedule 2004 2005 2006 2007 2008 2009 • Possible upgrade in future • 4MW Super-J-PARC + Hyper-K ( 1Mt water Cherenkov) • CP violation in lepton sector • Proton Decay K2K JHF-n construction physics run SK full rebuild MINOS OPERA/ICARUS 5yr (~20 nt)

25. Sensitivity (3s) to CP Violation Phase dwith upgrades • Bkg.subtraction with 2% accuracy（red), • bkg(2%)+selection(2%) (black) errors • Operation of 2 yr for nm and 6.8 yr for nm • d≧33deg at sin22q13=0.01 • d≧14deg for large sin22q13 • Understanding of background and systematics is essential Stat only Preliminary

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 q13 • precision measurement of q23, Dm232. • 1st 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 Linac Area

30. 3 GeV Area 3 GeV Area

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

32. 50 GeV 50 GeV