Long Baseline Neutrino Experiment in Japan

1. Long Baseline Neutrino Experiment in Japan T2K (Tokai to Kamioka Neutrino Oscillation Experiment) Neutrino facility becomes a reality in 3 years III International Workshop on “Neutrino Oscillations in Venice” Koichiro Nishikawa Kyoto University February 8, 2006

2. J-PARC Facility 500 m Neutrino to Kamiokande 3 GeV Synchrotron (25 Hz, 1MW) 50 GeV Synchrotron (0.75 MW) Linac (350m) Hadron Beam Facility Materials and Life Science Experimental Facility Nuclear Transmutation J-PARC = Japan Proton Accelerator Research Complex Joint Project between KEK and JAERI

3. Non-zero mass of neutrinos ! What kind of neutrino facility needed for years to come? Flavor Physics esp. history of neutrino studies show full of surprises ⇔ co op with unexpected ( Kamiokande for Kamioka Nucleon decay Experiment ! ) Quantities: lepton ID and neutrino energy En Good En determination Precision measurement of q23 Precision measurement of oscillation pattern⇒ oscillation + ? Lepton ID, NC-CC distinction e -appearance Dm2 ⇒MNS 3gen. formulation like CKM e-appearance exp. ⇒CPV in leptonic process (leptogenesis?) What is the best configuration for En and PID, given detector must be massive (simple) ?

4. Main features of T2K-1 The distance (295km) and Dm2 (~2.5x10-3 eV2 ) • Oscillation max. at sub-GeV neutrino energy • sub-GeV means QE dominant • Event-by event En reconstruction • Small high energy tail • small BKG in ne search and En reconstruction • Proper coverage of near detector(s) • Cross section ambiguity • Analysis of water Cherenkov detector data has accumulated almost twenty years of experience • K2K has demonstrated BG rejection in ne search • Realistic systematic errors and how to improve • Accumulation of technologies on high power beam

5. Phase2: 3~4 MW Phase2: Hyper-K Long baseline neutrino oscillation experiment from Tokai to Kamioka. (T2K) ~1GeV nm beam (100 of K2K) Super-K: 50 kton Water Cherenkov J-PARC 0.75MW 50GeV PS Kamioka Tokai Physics goals • Discovery ofnmneappearance • Precise meas. of disappearancenmnx 12 countries ~60 institutions ~180 collaborators • Discovery of CP violation (Phase2)

6. 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 En reconstruction at low energy • CC QE • can reconstruct En (qm,pm) • bkg. for En measurement High energy part • bkg.for e-appearance dE ~ 60 MeV dE/E ~ 10%

7. 1. Beam energy • Only the product F(E) x s(E) is observable • nm spectrum changes by oscil. • Sub-GeV small HE tail • CCQE dominates (1 process) • Even QE absolute cross section is known only with 20-30% precision • measurements at n production with similar spectrum are critical • Intermediate energy n flux should be kept to minimum • Many processes contribute (QE, 1p, 2p, DIS) • Spectrum changes causes mixture of processes changes 1 10 En

8. Super-K. q Decay Pipe Target Horns Narrow intense beam: Off-axis beam 振動確率＠ Dm2=3x10-3eV2 Anti-neutrinos by reversing Horn current OA0° nm flux p decay Kinematics OA2° OA2.5° 0° OA3° En (GeV) 1 2° 2.5° 3° 0 8 5 Statistics at SK (OAB 2.5 deg, 1 yr, 22.5 kt) ~ 2200nmtot ~ 1600nmCC ne~0.4% atnmpeak 0 2 pp (GeV/c) • Quasi Monochromatic Beam • x 2~3 intense than NBB • Tuned at oscillation maximum

9. Main features of T2K-1 The distance (295km) and Dm2 (~2.5x10-3 eV2 ) • Oscillation max. at sub-GeV neutrino energy • sub-GeV means QE dominant • Event-by event En reconstruction • Small high energy tail • small BKG in ne search and En reconstruction • Proper coverage of near detector(s) • Cross section ambiguity • Analysis of water Cherenkov detector data has accumulated almost twenty years of experience • K2K has demonstrated BG rejection in ne search • Realistic systematic errors and how to improve • Accumulation of technologies on high power beam

10. Experiences in K2K with Harp measurement • Neutrino cross section cannot be trusted above GeV and below deep inelastic region – • Proper near detectors to measure rate and Far/Near ratio should be used

11. Neutrino spectra at diff. dist 1.5km 295km 0.28km 2. Near detector complex Not approved yet p p n • Muon monitors @ ~140m • Fast (spill-by-spill) monitoring of beam direction/intensity (p→m n) • First near detector@280m • Flux/spectrum/ne - off-axis • intensity/direction - on-axis • Second near detector @ ~2km • Almost same En spectrum as for SK • facility request after commissioning of beam line • Far detector @ 295km • Super-Kamiokande (50kt) 0m 140m 280m 2 km 295 km 1 2 3 En GeV

12. Conceptual Design of Near Detector @ 280m Off-axis detector n spectrum Cross sect. ne contami. UA1 mag, FGD, TPC, Ecal,.. On axis detector Monitor beam dir. Grid layout Off-axis Detector Hole UA1 mag On-axis

13. Possible 2km detectors

14. Main features of T2K-1 The distance (295km) and Dm2 (~2.5x10-3 eV2 ) • Oscillation max. at sub-GeV neutrino energy • sub-GeV means QE dominant • Event-by event En reconstruction • Small high energy tail • small BKG in ne search and En reconstruction • Proper coverage of near detector(s) • Cross section ambiguity • Analysis of water Cherenkov detector data has accumulated almost twenty years of experience • K2K has demonstrated BG rejection in ne search • Realistic systematic errors and how to improve • Accumulation of technologies on high power beam

15. 3. PID in SK e-like m-like m e

16. Particle ID (e & m)(in single ring events) • An experiment with test beams confirmed the particle ID capability (PL B374(1996)238) m e Super-Kamiokande Atmosphric data

17. K2K 1KT data and MC reproducibility

18. SK data reduction in K2K real data: In total, #expected BG = 1.68 #observed = 1 nm (NC p0)BKG 1.3 events *1 Normalized by Nsk *2 different from std. PID (opening angle & ring pattern)

19. nm ne Search for nmne oscillation in K2K has achieved necessary p0 rejection • K2K real data with background rejection algorithm • As a result, • # of expected BG 1.68 events • (1.3 from nm & 0.38 from beam ne) • # of observed events 1 event T2K low energy beam, small tail 1/3 by HE tail – NC p0 1/3 by E rec Rough extrapolation to T2K x~100 nm 10,000 nm without osc. Shown by real data BKG ~1.3x100/9~15 for 5 years T2K

20. Sensitivities, precision in T2K phase-1

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

22. 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 2%)) • Spectrum shape (Fluka/MARS →(Near D.)) • Spectrum width (10%) OA2.5o d(sin22q23)~0.01 d(Dm223) <1×10-4 eV2

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

24. Sensitivity to q13 as a fuction of CP-phase d d d KASKA 90% (NuFact04) KASKA 90% (NuFact04) sin22q13 d →- for n →anti-n

25. Status of JPARC

26. 3 GeV RCS commissioning plan What about MR intensity? T2K construction

27. Intensity of MR • J-PARC start with 180 MeV LINAC Currently, following realistic scenarios have been studied • Intensity in 3 GeV Booster limited by space charge effect • increase number of bunches in MR by RF freq. increase in MR (injection time) • larger bucket in Booster to increase no. of protons/bunches • More RF powerto increase rep. (with money) • Every possible effort to increase MR intensity faster than 3GeV booster • Badget request will be submitted to restore 400 MeV LINAC (2008,9,10 ?) • Eventually more than MW beam

28. OR single bunch larger bucket (protons/bunch larger) keep h=9 (rep. rate is same as original

29. Accelerator commissioning plan 3 h.n.+RFx2 2 h.n. RF mod Beam Power (MW) Need upgrades of beam line elements 1 RCS power 0 2008 2009 2010 2011 2012 Japanese Fiscal Year (Apr-Mar)

30. Main features of T2K The distance (295km) and Dm2 (~2.5x10-3 eV2 ) • Oscillation max. at sub-GeV neutrino energy • sub-GeV means QE dominant • Event-by event En reconstruction • Small high energy tail • small BKG in ne search and En reconstruction • Proper coverage of near detector(s) • Cross section ambiguity • Analysis of water Cherenkov detector data has accumulated almost twenty years of experience • K2K has demonstrated BG rejection in ne search • Realistic systematic errors and how to improve • Accumulation of technologies on high power beam handling

31. First high enrgy MW fast-ext’ed beam ! 3.3E14 ppp w/ 5ms pulse When this beam hits an iron block, Residual radiation > 1000Sv/h cm cm 1100o (cf. melting point 1536o) • Material heavier than iron would melt. • Thermal shock stress (max stress ~300 MPa) Material heavier than Ti might be destroyed.

32. Special Features Superconducting combined function magnets Off-axis beam Components Primary proton beam line Normal conducting magnets Superconducting arc Proton beam monitors Target/Horn system Decay pipe (130m) Cover OA angle 2~3 deg. Beam dump muon monitors Near neutrino detector Neutrino Beam Line for T2K Experiment Target Station 130m decay volume 280m Beam dump/m-pit Near detector Construction: JFY2004~2008 To Super-Kamiokande

33. Schedule of T2K 2004 2005 2006 2007 2008 2009 • Possible upgrade in future →Next speaker • 4MW Super-J-PARC + Hyper-K ( 1Mt water Cherenkov) • CP violation in lepton sector • Proton Decay K2K T2K construction April 2009 n commissioning Linac SK full rebuild MR

34. Many new concepts emerged from studies of neutrinos. LH world Quark as physical constituent Number of generations Wide variety mass of elementary particles ……. Tradition will continue and New results in 2010