1. Water Cherenkov detector - brief status report - Kenji Kaneyuki Research Center for Cosmic Neutrinos, ICRR, Univ. of Tokyo

2. Summary of advantage and disadvantage advantage 50kt detector is already working Analysis method and its performance are established It is easy to enlarge detector compare to other one. Mton class detector are available A lot of physics topics proton decay, long baseline, atmospheric, solar, SN and relic neutrinos disadvantage Low track finding efficiency at high energy No magnetic field Super beam exp. Key issue is a cost ( photo detector ).

3. Photo Detector R&D in Japan (Tokyo and KEK) Aihara’s presentation at the 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam (July/13-14/2006) 13inch HPD prototype

4. Photo Detector R&D Aihara’s presentation at the 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam (July/13-14/2006) Time resolution for single photon

5. Aihara’s presentation at the 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam (July/13-14/2006)

6. Aihara’s presentation at the 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam (July/13-14/2006)

7. Aihara’s presentation at the 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam (July/13-14/2006)

8. Photo Detector R&D New photo detector R&D for Mton Water Cherenkov detector on AIL FJ-PPL will start. We will have a first workshop at KEK on Oct./3rd.

9. One of options of Mton detctor - T2KK - JPARC Off-axis angle 2.5deg.off-axis beam @Kamioka Distance from the target (km) K. Hagiwara Nucl. Phys. Proc. Suppl. 137 84 (2004) SK/HK 295km Korea ~1000km The 2 nd international Workshop on a Far detector in Koria for the J-Parc neutrino beam was held on July/13-14/2006 at SNU.

10. sin 2 2  13 =0.05 Merit of Korea detector: larger CP phase effect by a factor of 3 large energy dependence of P(   e ) vs P(   e ) Kamioka+Korea Better CP phase sensitivity and mass hierarchy  → e (  → e ) probability at Kamioka and Korea Okumura’s talk @ NuFact06

11. Conclusion Photo detector R&D goes steadily. 13inch HPD was developed. Readout electronics is under study. New photo detector R&D for Mton Water Cherenkov detector on FJ-PPL will start. T2KK is under study as a option of HK.