1. Takaaki Kajita ICRR, Univ. of Tokyo Nufact05, Frascati, June 2005 Based on reports at NNN05 Next generation of Nucleon decay and Neutrino detectors http://nnn05.in2p3.fr/

2. Outline Introduction Neutrino oscillation physics with super-beams (This topic should be discussed extensively in this workshop.  Skip.) Neutrino oscillation physics with atmospheric neutrinos Neutrino physics with atmospheric neutrinos + super-beams Solar and supernova neutrinos A Mton water detector with Gd Proton decay R&D Summary Apology: references incomplete…

3. Present: Study of dominant oscillation channels Future: Study of sub-dominant oscillations e     3 2 1 Solar, KamLAND Atmospheric Long baseline  12,  m 12 2 Known: Unknown:   13 Sign of  m 2 or CP ? If  23 ≠  /4, is it >  /4 or <  /4 ?  23, |  m 23 2 | Future Mton class detector

4. Future long baseline neutrino experiments - example - J-PARC ＢＮＬ  -beam UNO MEMPHYS Hyper-K Megawatt class super (or  )-beam + Megaton class water detector Fermilab NuMI Hierarchy, CP, …. Refs: many talks at NNN05 Many, many talks in this meeting

5. Neutrino oscillation physics with atmospheric neutrinos Sign of  m 23 2 Is  23 >  /4 or <  /4 ? Sign of  m 23 2 Is  23 >  /4 or <  /4 ? TK NNN05 Long neutrino flight length in matter Very wide L/E  solar L/E range is relevant Long neutrino flight length in matter Very wide L/E  solar L/E range is relevant Atmospheric neutrino beam :

6. Sign of  m 2 ? Single-ring e-like Multi-ring e-like Positive  m 2 Negative Dm 2 null oscillation cos  Relatively high anti- e fraction More events if  m 2 <0 Relatively high e fraction More events if  m 2 >0  m 2 =0.002eV 2 s 2  23 = 0.5 s 2  13 = 0.05 (0.45 Mtonyr) If  m 23 2 is positive, resonance for neutrinos If  m 23 2 is negative, resonance for anti-neutrinos E (GeV) cos 

7.  2 difference (inverted-normal)  m 2 : fixed,  23 : free,  13 : free Exposure: 1.8Mtonyr 33 33 33 True= normal mass hierarchy assumed. (A similar but slightly worse sensitivity for inverted mass hierarchy.)

8. s 2 2  12 =0.825  m 2 12 =8.3×10 -5  m 2 23 =2.5×10 -3 sin 2  13 =0 Because of the LMA solution, atmospheric neutrinos should also oscillate by (  12,  m 12 2 ). Oscillation probability is different between s 2  23 =0.4 and 0.6  discrimination between  23 >  /4 and <  /4 might be possible. s 2  23 =0.4 =0.5 =0.6 However, due to the cancellation between   e and e  , the change in the e flux is small. Peres & Smirnov NPB 680 (2004) 479 Solar term effect to atmospheric Solar term effect to atmospheric

9. Discrimination between  23 >  /4 and  /4 and <  /4 with the (12) and (13) terms s 2  23 =0.40 ~ 0.60 s 2  13 =0.00~0.04  cp=45 o Discrimination between  23 >  /4 and <  /4 is possible for all  13. 1.8Mtonyr Discrimination between  23 >  /4 and 0.04. sin 2  23 sin 2  13 sin 2 2  23 =0.96sin 2 2  23 =0.99 90%CL Test point Fit result

10. Neutrino physics with atmospheric neutrinos + super beams T.Schwetz NNN05, also in this meeting, Huber, Maltoni, Schwetz hep-ph/0501037 Parameter degeneracies in T2K-II Atmospheric neutrinos: Sensitive to mass hierarchy and octant of  23 Combine LBL and atm data to resolve the degeneracies

11. Resolving the degeneracies  4MW beam, 2yr neutrino run, 6yr anti-neutrino run, 1Mton detector at 295km  9Mtonyr atmospheric neutrino data

12. Identifying the mass hierarchy s 2  23 =0.5 assumed Atm only LBL only 1  2  3  LBL+atm

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

14. Expected signal 8 B spectrum distortion Enough statistics to see distortion. Energy scale calibration should be better than ~0.3%. E e (MeV) Data/SSM 5 Mton·years Correlated sys. error of SK sin 2  =0.28,  m 2 =8.3×10 -5 eV 2 1/2 of SK Day-night stat. significance 3  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.

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

16. Supernova shock and neutrino oscillations Assume: nature = inverted hierarchy Anti- e If sudden change in the average energy is observed  Inverted mass hierarchy and sin 2  13 >10 -5. sin 2  13 Forward shock Reverse shock  m 13 2 resonance  m 12 2 resonance A.Dighe NNN05 R.Tomas et al., astro-ph/0407132

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

18. Supernova relic neutrinos (SRN) SRN prediction SK result e +anti- e Invisible   e SNR limit 90%CL 90%CL limit: 1.2 /cm 2 /sec (E >19MeV) (which is just above the most recent prediction 1.1/cm 2 /sec)  get information on galaxy evolution and cosmic star formation rate With a Mton detector, it must be possible to see SRN signal S.Ando, M.Nakahata NNN05

19. Mton detector with Gd loaded water GADZOOKS! M.Vagins NNN05 B.G. reduction by neutron tagging No neutron tagging Statistically 4.6  excess (E vis > 15 MeV) Simulation: M.Nakahta NNN05 (0.2% GdCl 3 ) M.Vagins, J.Beacom hep-ph/0309300 Invisible   e

20. Search for proton decay Lifetime in benchmark scenarios J.Ellis NNN05 C.K.Jung NNN05 How long is the predicted proton lifetime ? SK limit (e  0 ) SK limit ( K + )

21. Search for p  e +  0 P tot < 250 MeV/c, BG 2.2ev/Mtyr, eff=44% P tot < 100 MeV/c, BG 0.15ev/Mtyr, eff=17.4% Atm 20Mtonyr free proton decay bound proton decay Main target is free proton decays for the tight cut. p  e  0 Monte Carlo e+e+ e+e+  0   M.Shiozawa NNN05

22. Lifetime sensitivity for p  e +  0 Normal cut, 90%CL 3  CL Tight cut, 90%CL 3  CL p  e+  0 sensitivity 5Mtonyrs  ~10 35 years@90%CL ~4x10 34 years@3  CL 5Mtonyrs

23. νK + sensitivity (based on SK criteria) τ/B > 2 × 10 34 yr (5Mtonyr, 90%CL) Question: How much photo cathode coverage is necessary? Most updated number = 2,3×10 33 yrs 5Mtonyrs 12nsec 2.2  sec

24. Remarks on R&D Photo-detector and excavation are the most important items for the construction of the Mton detector. My impression at NNN05 ◆ Excavation of an underground cavity for a Mton class detector seems to be possible, but more site specific R&D are necessary. ◆ Photo-detector R&D are going on, but it is still unclear if a much cheaper (and better) photo-detector can be ready by the time of the start of the construction.  More R&D are necessary. ◆ Also, a more serious discussion on the physics of Mton detector and the detector design might be necessary. One example: what will be the optimal photo-cathode coverage, 10, 20 or 40% ? ◆ Excavation of an underground cavity for a Mton class detector seems to be possible, but more site specific R&D are necessary. ◆ Photo-detector R&D are going on, but it is still unclear if a much cheaper (and better) photo-detector can be ready by the time of the start of the construction.  More R&D are necessary. ◆ Also, a more serious discussion on the physics of Mton detector and the detector design might be necessary. One example: what will be the optimal photo-cathode coverage, 10, 20 or 40% ? It is very good that it was decided to have the NNN workshop every year. (Aihara, Ferenc, Pouthas, Hamamatsu, Photonics, Electron tubes, NNN05) (Jung, Nakagawa, Levy, Duffaut, NNN05)

25. A Mton water detector will be an excellent neutrino detector for super-beam experiments. (This was not discussed in this talk.) A Mton water detector will have a lot of physics opportunities. A Mton detector can not be cheap. Therefore it is very nice that it can carry out many important physics. Serious detector R&D are necessary.

26. End

27.  2 difference (normal – inverted)  m 2 : fixed,  23 : free,  13 : free Exposure: 1.8Mtonyr 33 33 33 True= inverted mass hierarchy assumed.

28. Effect of the solar term to sub-GeV e-like zenith angle sub-GeV e-like  m 2 12 = 8.3 x 10 -5 eV 2  m 2 23 = 2.5 x 10 -3 eV 2 sin 2 2  12 = 0.82 sin 2  23 = 0.4 sin 2  23 = 0.5 sin 2  23 = 0.6 (P e :100 ~ 1330 MeV)(P e :100 ~ 400 MeV)(P e :400 ~ 1330 MeV) cos  zenith N_e (3 flavor) / N_e (2 flavor full-mixing) (Much smaller and opposite effect for  -like events.)  /e ratio @low energy is useful to discriminate  23 >  /4 and <  /4.