Soo-Bong Kim, Seoul National University, sbkim@phya.snu.ac.kr

1. NNN07 at Hamamatsu, Oct. 2-5, 2007 Report of the T2KK Workshop Soo-Bong Kim, Seoul National University, sbkim@phya.snu.ac.kr

2. http://T2KK.snu.ac.kr 1st & 2nd Workshops on T2KK http://newton.kias.re.kr/~hepph/J2K

3. Summary of the 1st & 2nd Workshops • T2KK motivation: • - T2K-II with HK needs to resolve the degeneracy in the measured CP • phase based on the longer L and the larger matter effects • Location of the detector(s): • - ~2000 m.w.e. depth for most of physics (H.Sobel, T2KK05) • - a candidate site at Kamioka (K.Nakamura, T2KK05) • - mountains of 1,200 meters in height are found almost everywhere in • the interesting region of Korea (D.Son, T2KK05, C.Ryu, T2KK06) • Resolving the oscillation parameter degeneracy: • - mass hierarchy & CP phase (H.Minakata, N.Okamura, E.J.Jeon, T2KK05 • S.K.Kang, H.Minakata, K.Senda, T2KK06) • - sensitivity as a function of off-axis angle at far detector (N.Okamura, T2KK05/06, • F.Dufour, T2KK06, K.Okumura, T2KK06, A.Rubbia, T2KK05/06) • - liquid Ar sensitivity (A.Rubbia, T2KK05/06) • Probing non standard physics: • - NSI (P.Ko, H.Sugiyama, T2KK06) • - test of unitarity (B.Gavela, T2KK06)

4. University of Tokyo, Tokyo 9/30-10/1, 2007 • Site study for HK and one in Korea (N. Wakabayashi, C. Ryu) • BNL-Fermilab LBL/J-PARC /Systematics at Superbeam exp. (M. Diwan, T. Ishida, P. Huber) • Oscillation parameter degeneracy (S.K. Kang, J. Valle) • T2KK sensitivity in resolving degeneracy (F. Dufour, C. Ishihara, N. Okamura, K. Okumura, A. Rubbia, K. Senda) • NSP/Test of Unitarity (P. Ko, K. Kimura) 4th workshop at KIAS, Seoul fall, 2008 3rd Workshop on T2KK http://www-rccn.icrr.u-tokyo.ac.jp/workshop/T2KK07/

5. Site Study for Hyper-Kamiokande • Site studies and cavern analyses by Mitsui Mining & Smelting Co. Ltd. (K. Nakamura, T2KK05) • Study on the joint rock mass by Shimizu Corporation (N. Wakabayashi, T2KK07)

6. Site Study for the Korean Detector • mountains of 1,200 meters in height are found almost everywhere in • the interesting region of Korea → Search for a candidate site • (D.Son, T2KK05, C.Ryu, T2KK06/07)

7. Oscillation Parameter Degeneracy • Resolving the octant degeneracy (H. Minakata, T2KK05/06, S.K.Kang T2KK06/07) If q23 ≠p/4, is it >p/4 or <p/4 ? q13 Sign of Dm232 nenmnt or n3 nenmnt n3 n2 n1 or n3 CP ? How much can T2KK contribute to these measurements?

8. Detect solar m2 effect (∝cos223) • Requires very long baseline (or very large L/E) • OK even at small 13 • (S. Nakayama T2KK06) • Combining reactor measurement of 13 • Requires great precision in reactor 13 measurement • Powerful at large 13 • (N. Okamura T2KK06) Very large L/E + Reactor 13 (C. Ishihara, N. Okamura, A. Rubbia, T2KK07) How to solve the octant degeneracy? H. Minakata, T2KK06 Strategy: Use information which are not proportional to sin2223 x sin2213

9. Sensitivity of Mass Hierarchy C. Ishihara, T2KK07

10. Resolving the degeneracy: T2K-II vs. T2KK T2K-II (Kamioka only) T2KK (Kamioka + Korea) Octant of q23 not resolved Mass hierarchy not determined T2KK has a good sensitivity to resolve the parameter degeneracies.

11. sin22q13 Sensitivity to the Octant of 23 S. Nakayama, T2KK06 sin22q23=0.96 OA 2.5 degree for both Kamioka and Korea sin22q23=0.99 2s 3s Octant ambiguity of q23 can be resolved at 2sif sin22q23 < ~0.97 (almost independent of the value of sin22q13 and mass hierarchy). T2KK could resolve the 8 hold degeneracy of the oscillation parameters.

12. Sensitivity on Off-axis Angles of the Korea Detector N.Okamura, T2KK05/07 Suggested that the higher energy beam is better due to the larger matter effect. 1.0 to 3.0 degree off-axis beam available in Korea. • However, background might be a serious issue for higher energy beam. • Detailed Monte Carlo study (F.Dufour, T2KK06) • Liquid Argon detector (A.Rubbia, T2KK05/06)

13. The sensitivity does not depend strongly on L ! Potentially many candidate sites ! Sensitivity on Baseline of the Korea Detector K. Okumura, T2KK06 2.5 degree off-axis beam with L between 1,000km and 1,250km is available. Kamioka only L=1000km L=1050km L=1100km L=1150km L=1200km L=1250km sin22q13 3 s sensitivity to mass hierarchy (True = normal hierarchy) d

14. Beam Energy Profiles at Sites in Korea A. Rubbia, T2KK07 1.0 to 3.0 degree off-axis beam available in Korea.

15. Signal & BG for Various Off-axis Beams F.Dufour, T2KK06 Korea Kamioka 1.5 degree 1.0 degree 2.5 degree signal signal BG BG sin2(2q13)=0.1 d=1/2p 4 year neutrino run 4MW beam 2.5 degree 2.0 degree • Smaller off-axis angle: • Larger matter effect at the 1st osc. Max.. •  Low E BG more serious. • (2nd osc. Max. difficult to see.)

16. T2KK Sensitivities for Various OA Angles F.Dufour, T2KK06/07 Mass hierarchy CP violation

17. Sensitivity of Mass Hierarchy A. Rubbia, T2KK07 • The longer baseline & higher rate improves mass hierarchy determination

18. Liquid Ar Detector A. Rubbia, T2KK05/06/07 Deep inelastic Quasi-elastic • Possibility to study exclusive final states also in Multi-GeV range • Detector behaves as a very fine-grained “tracking-calorimeter” Very small NC and other ne background even with the multi-GeV beam.  Good for near on-axis beam.

19. Sensitivity of Liquid Ar Detector A. Rubbia, T2KK05/06/07 OA 1.0 deg, 28×1021pot, 100 kton mass Very high sensitivity, especially in the very small sin22q13 region. sin22q13=0.006 Mass Hierarchy CP

20. Probing Non-standard Neutrino Physics P. Ko, T2KK06/07 • Quantum Decoherence: • Lorentz Symmetry/CPT Violation: • Flavor nonuniversal neutrino interactions with matter: See their upcoming paper….

21. Summary • T2KK is an interesting option to resolve the oscillation parameter degeneracy based on the longer baseline and an additional, identical detector in Korea. • For the best experiment, T2KK needs further tuning of some of parameters such as baseline, off-axis angle, detector mass, etc. • T2KK needs a study of more physics opportunities.