Takaaki Kajita ICRR, Univ. of Tokyo

1. KIAS, Seoul, Nov. 2005 Non LBL physics with large water Cherenkov detectors Takaaki Kajita ICRR, Univ. of Tokyo Fig: Senda NP-4

2. Non-LBL physics with large water Cherenkov detectors • Atmospheric neutrinos (300 events /day) • Proton decay • Supernova neutrinos (200,000 events for SN @galactic center) • Supernova relic neutrinos • Solar neutrinos (300-400 events/day) • ……

3. Outline • Assumptions • Neutrino oscillation physics with atmospheric neutrinos • Proton decay • Comment on photo cathode coverage • Summary Apology: references incomplete…

4. Assumptions Distance from the target (km) Off-axis angle JPARC Fig: Talk by K.Senda @NP04 (also, hep-ph/0504061) • Fid. MassKamioka+Korea=0.54 Mton • Detector performance = Super-K

5. Neutrino oscillation physics with atmospheric neutrinos TK NNN05

6. mass and mixing parameters: q12, q23, q13, d, Dm122, Dm132(=Dm232) q12, Dm122 q23, |Dm232| Known: nenmnt n3 Solar, KamLAND Atmospheric Long baseline n2 n1 KamLAND SNO(+Super-K) Super-K K2K Reactor solar atmospheric long baseline

7. mass and mixing parameters: q12, q23, q13, d, Dm122, Dm132(=Dm232) Near future reactor, LBL exp’s Unknown: If q23 ≠p/4, is it >p/4 or <p/4 ? q13 Sign of Dm232 nenmnt n3 nenmnt n3 or n2 or n1 n3 CP ? Atmospheric neutrino experiments Future long baseline eperiments  JPARC-Kamioka-Korea (Atmospheric neutrino exp.s could help….)

8. Solar term effect to atmospheric n Peres & Smirnov NPB 680 (2004) 479 Because of the LMA solution, atmospheric neutrinos should also oscillate by (q12, Dm122). s22q12=0.825 Dm212=8.3×10-5 Dm223=2.5×10-3 sin2q13=0 However, due to the cancellation between nmne and nenm, the change in the ne flux is small. Oscillation probability is different between s2q23=0.4 and 0.6  discrimination between q23 >p/4 and <p/4 might be possible.

9. Effect of the solar term to sub-GeV e-like zenith angle Dm212 = 8.3 x 10-5 eV2 Dm223 = 2.5 x 10-3 eV2 sin2 2q12 = 0.82 sin2q13=0 sub-GeV e-like (Pe :100 ~ 1330 MeV) (Pe :100 ~ 400 MeV) (Pe :400 ~ 1330 MeV) sin2 q23 = 0.4 sin2 q23 = 0.5 sin2 q23 = 0.6 e-like (3 flavor) / e-like (2 flavor full-mixing) cosqzenith (Much smaller and opposite effect for m-like events.) m/e ratio @low energy is useful to discriminate q23>p/4 and <p/4.

10. (m/e) (3 flavor) (m/e) (2 flavor full-mixing) Effect of the solar terms to the sub-GeV m/e ratio (zenith angle dependence) Dm212 = 8.3 x 10-5 eV2 Dm223 = 2.5 x 10-3 eV2 sin2 2q12 = 0.82 sin2q13=0 sub-GeV Pm , e < 400 MeV Pm , e > 400 MeV sin2q23 = 0.6 2 flavor (sin22q23=.96) sin2q23 = 0.5 sin2q23 = 0.4 It could be possible to discriminate the octant of q23, if sin2q23 is significantly away from 0.5.

11. Expected oscillation with solar terms (2) s22q12=0.825 Dm212=8.3×10-5 Dm223=2.5×10-3 In addition, we may have non-zero q13. s2q23=0.4 s2q13=0.04 dcp=p/4 s2q23=0.4 s2q13=0.0 Effect of q13 Interference (CP) Effect of LMA = 1 + P2 (r cos2q23 – 1) P2 = 2n transition probability ne  nmt in matter driven by Dm122

12. 0.45 Mtonyr 3s Search for non-zero q13 Electron appearance 1+multi-ring, e-like, 2.5 - 5 GeV 0.45Mtonyr s213=0.05 s213=0.00 null oscillation (Dm122=0 assumed) cosQ Matter effect cosqzenith Approximate CHOOZ bound En(GeV)

13. Binning for this study (= osc. analysis in SK) 10 zenith angle bins for each box. Sub-GeV Multi-GeV Up-stop Single-Ring m Multi-Ring m PC- stop Single-Ring e Multi-Ring e PC- through Up-through En CC ne CC nm 37 momentum bins x 10 zenith bins = 370 bins in total Small number of events per bin For more details: please ask H.K.Seo and S.Nakayama Poisson statistics to claculate c2 with 45 systematic error terms

14. n3 n2 n1 sin2q13 sin2q23 0.092 Mtonyr Super-K data cosqzenith Analysis with and w/o solar terms Search for non-zero q13 En(GeV) with 12 terns (best fit s2q23 = 0.51) w/o 12

15. M.Shiozawa et al, RCCN Int. Workshop on sub-dom. Atm. Osc. 2004 Discrimination between q23 >p/4 and <p/4 with the (12) and (13) terms s2q23=0.40 ~ 0.60 s2q13=0.00~0.04 dcp=45o 1.8Mtonyr (or 3.3yr×0.54Mton) 90%CL 90%CL sin22q23=0.96 sin22q23=0.99 Fit result Test point sin2q13 sin2q23 sin2q23 Discrimination between q23>p/4 and <p/4 is possible for all q13. Discrimination between q23>p/4 and <p/4 is marginally possible only for s2q13 >0.04.

16. (m/e) (3 flavor) (m/e) (2 flavor full-mixing) 0.8 Mtonyr = SK 20yr = HK 0.8yr Improvement possible ? S.Nakayama, RCCN Int. Workshop on sub-dom. Atm. Osc. 2004 Dm212 = 8.3 x 10-5 eV2 Dm223 = 2.5 x 10-3 eV2 sin2 2q12 = 0.82 sin2q13=0 true Pm , e < 400 MeV sin2q23 = 0.6 2 flavor (sin22q23=.96) sin2q23 = 0.5 sin2q23 = 0.4

17. Search for proton decay How long is the predicted proton lifetime ? C.K.Jung NNN05 J.Ellis NNN05 Lifetime in benchmark scenarios SK limit (ep0) SK limit (nK+)

18. Ptot < 250 MeV/c, BG 2.2ev/Mtyr, eff=40% • Ptot < 100 MeV/c, BG 0.15ev/Mtyr, eff=17% Search for pge+p0 pep0 Monte Carlo M.Shiozawa NNN05 e+ p0gg Main target is free proton decays for the tight cut. Atm n 20Mtonyr bound proton decay free proton decay Now (near future) Future

19. Lifetime sensitivity for pge+p0 pge+p0 sensitivity 5Mtonyrs 5Mtonyrs  ~1035 years@90%CL ~4x1034 years@3sCL Normal cut, 90%CL 3s CL Tight cut, 90%CL 3s CL

20. pnK+ NPMT-hit distribution for the prompt gamma search (1)16OnK+15Ng, K+→m+n e+nn Signal region 236MeV/c 6 – 10 MeV (Also, searches for (2) pnK+ (K+p+p0) (3) PnK+(K+m+n, without g) ) Background = 0.7 e = 8.6% Candidate = 0

21. 12nsec 2.2msec νK+ sensitivity (based on SK criteria) 5Mtonyrs τ/B > 2 × 1034yr (5Mtonyr, 90%CL) Most updated number = 2,3×1033 yrs Question: How much photo cathode coverage is necessary?

22. Photo cathode coverage ? • Cost for the photo-detectors is a significant part of the total detector cost. • If 40% coverage with 50cm diameter PMT’s for 0.27 Mton fiducial mass; •  100,000 PMT’s. •  If 100 (200?) $ / PMT  100M$ (200?M$) • Important to understand minimum requirement of photo-coverage from each physics topics • SK-II (19% coverage  SK-I 40%) is a good opportunity • to investigate physics sensitivity with reduced photo- • coverage. •  LBL physics •  Atmospheric neutrinos •  Proton decay (ep0)  This talk •  Proton decay (nK+) • Astrophysical neutrinos (SN, solar neutrinos? ...)

23. Proton mass vs. momentum atmn(BG) MC pgep0 MC SK-I e=40.1% SK-I 8 /2.2Mtyr SK-II e=41.1% SK-II 2 /0.45Mtyr

24. Proton mass and momentum pgep0 MC SK-I SK-I SK-II SK-II p mass resolution; 33.8MeV42.3 (free proton) 28.5MeV35.2 p mom. resolution; 177MeV(68%)171 ( free proton) 81MeV(68%)83  pep0 looks OK with 20% photo cathode coverage.

25. Photo cathode coverage ? •  LBL physics Need careful checks •  Atmospheric neutrinos  20% probably OK. • (No proof today…) •  Proton decay (ep0)  20% looks OK. •  Proton decay (nK+) We will know in a • month or half a year… • Astrophysical neutrinos (SN, solar n? ...) • Need checks…

26. Summary • Mton class water detectors will have a lot of physics opportunities. • Mton class detectors can not be cheap. Therefore it is very nice that it could carry out many important physics.

27. End

28. Solar+KamLAND 99.73% 95% Vacuum osc. dominant KamLAND P(ne ne) Solar global matter osc. (MeV) Solar neutrino physics with Mton detectors M.Nakahata NNN05 Do we want further evidence for matter effect ? Day-night asymmetry

29. sin2q=0.28, Dm2 =8.3×10-5 eV2 Expected signal 8B spectrum distortion Day-night stat. significance Correlated sys. error of SK 1/2 of SK Data/SSM 5 Mton·years Ee (MeV) Enough statistics to see distortion. Energy scale calibration should be better than ~0.3%. 3s signal can be obtained with 0.5% day-night systematic error. In both cases, systematic errors or background are assumed to be better than SK.

30. Supernova events in a Mega-ton detector A.Dighe NNN05 ◆Initial spectra rather poorly known. ◆Only anti-ne observed • Difficult find a “clean” observable, which is (almost) independent of the assumptions on the initial spectra. Number of anti-ne+p interactions = 200,000 - 300,000 for a galactic Supernova (@10kpc)

31. Reverse shock Forward shock Dm132 resonance Dm122 resonance Supernova shock and neutrino oscillations Assume: nature = inverted hierarchy Anti-ne sin2q13 If sudden change in the average energy is observed  Inverted mass hierarchy and sin2q13>10-5. A.Dighe NNN05 R.Tomas et al., astro-ph/0407132

32. S.Ando NNN05 Mton is large: The detectors can see extragalactic SNe Nearby SN rate Detection probability SK HK

33. S.Ando, M.Nakahata NNN05 SRN prediction Supernova relic neutrinos (SRN)  get information on galaxy evolution and cosmic star formation rate SK result SNR limit 90%CL Invisible m e ne+anti-ne 90%CL limit: 1.2 /cm2/sec (En>19MeV) (which is just above the most recent prediction 1.1/cm2/sec) With a Mton detector, it must be possible to see SRN signal

34. Mton detector with Gd loaded water GADZOOKS! M.Vagins NNN05 M.Vagins, J.Beacom hep-ph/0309300 Simulation: M.Nakahta NNN05 (0.2% GdCl3) No neutron tagging B.G. reduction by neutron tagging Invisible m e Statistically 4.6s excess (Evis > 15 MeV)

35. End

36. (0, Free parameter) Flux, Nu-int, Fit; absolute normalization (1) Flux; (nu_mu + anti-nu_mu) / (nu_e + anti-nu_e) ratio ( E_nu < 5GeV ) (2) Flux; (nu_mu + anti-nu_mu) / (nu_e + anti-nu_e) ratio ( E_nu > 5GeV ) (3) Flux; anti-nu_e / nu_e ratio ( E_nu < 10GeV ) (4) Flux; anti-nu_e / nu_e ratio ( E_nu > 10GeV ) (5) Flux; anti-nu_mu / nu_mu ratio ( E_nu < 10GeV ) (6) Flux; anti-nu_mu / nu_mu ratio ( E_nu > 10GeV ) (7) Flux; up/down ratio (8) Flux; horizontal/vertical ratio (9) Flux; K/pi ratio (10)flight length of neutrinos (11) spectral index of primary cosmic ray above 100GeV (12) sample-by-sample relative normalization ( FC Multi-GeV ) (13) sample-by-sample relative normalization ( PC + Up-stop mu ) (14) MA in QE and single-p (15) QE models (Fermi-gas vs. Oset's) (16) QE cross-section (17) Single-meson cross-section (18) DIS models (GRV vs. Bodek's model) (19) DIS cross-section (20) Coherent-p cross-section (21) NC/CC ratio (22) nuclear effect in 16O (23) pion spectrum (24) CC ntcross-section 45 systematic error terms Flux (13) Detector, reduction and reconstruction (20) (25) Reduction for FC (26) Reduction for PC (27) Reduction for upward-going muon (28) FC/PC separation (29) Hadron simulation (contamination of NC in 1-ring m-like) (30) Non-n BG ( flasher for e-like ) (31) Non-n BG ( cosmic ray muon for mu-like ) (32) Upward stopping/through-going mu separation (33) Ring separation (34) Particle identification for 1-ring samples (35) Particle identification for multi-ring samples (36) Energy calibration (37) Energy cut for upward stopping muon (38) Up/down symmetry of energy calibration (39) BG subtraction of up through m (40) BG subtraction of up stop m (41) Non-necontaminationformulti-GeV 1-ringelectron (42) Non-necontaminationformulti-GeV multi-ringelectron (43) Normalizationofmulti-GeV multi-ringelectron (44) PC stop/through separation ninteraction (11)

37. sub-GeV m-like zenith angle X : zenith angle Y : N_m (3 flavor) / N_m (2 flavor full-mixing) sub-GeV m-like (Pm : 200 ~ 1330 MeV) (Pm : 200 ~ 400 MeV) (Pm : 400 ~ 1330 MeV) sin2 q23 = 0.4 sin2 q23 = 0.5 sin2 q23 = 0.6 2 flavor (sin2 2q23 = 0.96) Dm212 = 8.3 x 10-5 eV2 Dm223 = 2.5 x 10-3 eV2 sin2 2q12 = 0.82

38. Discrimination between q23 >p/4 and <p/4 with the (12) and (13) terms s2q23=0.40 ~ 0.60 s2q13=0.00~0.04 dcp=45o 1.8Mtonyr = SK 80 yrs = 3.3 HK yrs 90%CL 90%CL sin22q23=0.96 sin22q23=0.99 Fit result Test point sin2q13 sin2q23 sin2q23 Discrimination between q23>p/4 and <p/4 is possible for all q13. Discrimination between q23>p/4 and <p/4 is marginally possible only for q13 >0.04.