1. Road Map of Neutrino Physics in Japan Largely my personal view Don’t take too seriously K. Nakamura KEK NuFact04 July 30, 2004

2. Road Map of Neutrino Physics in Japan Ongoing Super-Kamiokande K2K KamLAND Constructing T2K @ J-PARC R&D Hyper-Kamiokande XMASS FFAG for Neutrino Factory Proposed KASKA Double  decay exp. 42m 39m C Scientific American

3. T2K Phase I: Measurement of sin 2 2θ 13 sin 2θ 13 ν μ (CC+NC) Bean ν e Osc ’ d ν e Signal+BG 0.111.1 123.2145.5 0.0111.1 12.334.5 2 sin 2 2θ 13 Δm 2 ×1/20 CHOO Z limit JHF sensitivity Expected signal for OA 2deg 5yrs sin 2 2  13 =0.1

4. Sensitivity for  13 sin 2 2  13 ~0.006 (90%) sin 2 2  13 < 10 -3 can be searched if syst err ~ few % 0.5xsin 2 2  13 sin 2 2  13 ~0.018 (3  )

5. 3  CP sensitivity : |  |>20 o for sin 2 2  13 >0.01 with 2% syst. 4MW, 540kt 2yr for  6~7yr for   m 21 2 =6.9x10 -5 eV 2  m 32 2 =2.8x10 -3 eV 2  12 =0.594  23 =  /4 T2K-I 90% no BG signal stat only (signal+BG) stat only stat+2%syst. stat+5%syst. stat+10%syst. CHOOZ excluded sin 2 2  13 <0.12@  m 31 2 ~3x10 -3 eV 2 T2K 3  discovery T2K: CP Violation Sensitivity

6. Possible Phase 2 Intensity Upgrade of the J-PARC 50 GeV Ring Ramping speed → 0.89 Hz Lattice magnet designed this way Barrier bucket Decreases the local line density at injection Reduces the space charge effect

7. 2 detectors×48m × 50m ×250m, Total mass = 1 Mton Twin Detector Hyper-Kamiokande

8. Wished Construction Plan 2008 09 20 10 11 12 13 14 20 15 16 17 18 1920 21 22 23 T2K-I HK construction HK experiment

9. 9 Japanese FFAG Scheme

10. 10 Nufact at J-PARC

11. 11 Staging Approach towards Realization

12. Long Baselines ? J-PARC Seoul Beijing Fukuoka Shanghai Or Hawaii ?

13. 13 Construction of the PRISM-FFAG

14. 14 Pulsed proton beam facility

15. Road Map of Neutrino Physics in Japan Neutrino CP Violation (If  >20 deg) Measurement of  13 J-PARC Hyper-K T2K Phase II J-PARC Intensity Upgrade T2K Phase I Measurement of sgn(  m 23 2 ) FFAG R&D Neutrino factory If  13 is not too small (sin 2 2  13 > 0.02) We are here. Super-K K2K T2K KamLAND KASKA XMASS Precision measurements of  m 23 2,  23,  m 12 2, (  12 )

16. How can we discriminate positive and negative  m 2 ? Real  m 2 = positive assumed (No resonance for anti-neutrinos) Real  m 2 = negative assumed (No resonance for neutrinos) E (GeV) cos  P(   e ) E (GeV) cos  P(   e )

17. How can we discriminate neutrino and anti- neutrino interactions ? Simple answer: No. It is not possible to discriminate event by event in water Cherenkov experiments. However,  (total) and d  /dy are different.  Try to discriminate positive and negative  m 2 using these events. CC e Others Single-ring e-likeMulti-ring e-like

18. Electron appearance for positive and negative  m 2 Single-ring e-likeMulti-ring e-like Positive  m 2 Negative Dm 2 null oscillation cos  Relatively high anti- e fraction Lower anti- e fraction  m 2 =0.002eV 2 s 2  23 = 0.5 s 2  13 = 0.05 (SK 20yrs)

19.  2 difference (inverted-normal)  m 2 : fixed,  23 : free,  13 : free Exposure: 1.8Mtonyr (SK 80yr or HK ～ 3.3 yr) 33 33 33 True= normal mass hierarchy assumed.

20.  2 difference (normal – inverted)  m 2 : fixed,  23 : free,  13 : free Exposure: 1.8Mtonyr (SK 80yr or HK ～ 3.3 yr) 33 33 33 True= inverted mass hierarchy assumed.

21. We are here. Super-K K2K T2K 90% CL Upper Limit of  13 J-PARC T2K Phase I Road Map of Neutrino Physics in Japan J-PARC Intensity Upgrade Measurement of  13 Hyper-K T2K Phase II Neutrino CP Violation (If  >20 deg, Sin 2 2  13 >0.01 ) FFAG R&D Neutrino factory If  13 is small (0.006 < sin 2 2  13 < 0.02)

22. Road Map of Neutrino Physics in Japan We are here. Super-K K2K T2K  13 ≠0 cannot be established J-PARC T2K Phase I J-PARC Intensity Upgrade? Hyper-K? T2K Phase II? FFAG R&D Neutrino factory If  13 is too small (sin 2 2  13 < 0.006)

23. Road Map of Neutrino Physics in Japan Summary (Most Optimistic Case) 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 K2K Super-K / Hyper-K T2K J-PARC 50 GeV FFAG R&D finished Full reconstruction construction construction completed completed low intensity full intensity Phase I   construction Phase 1.5 (CP) - Phase II CP Intensity upgrade P decay Atmospheric PRISM-I @J-PARC PRISM-II @J-PARC Neutrino Factory ？