TAUP 07 Sep 2007 Sendai Takaaki Kajita ICRR

TAUP 07, Sep. 2007, Sendai Takaaki Kajita, ICRR, Univ. of Tokyo ◆Introduction ◆T 2 KK @TAUP 05 ◆Updating T 2 KK - L dependence, - Higher energy option, - Octant of q 23, ◆Summary

sin 2 q 12, sin 22 q 23, Dm 122, |=Dm 232|・・・・ Already measured. Let’s assume that non-zero q 13 will be observed by the next generation oscillation experiments. n 3 q 13 ne nm nt Sign of Dm 232 If q 23 ≠p/4, is it >p/4 or <p/4 ? n 3 n 2 n 1 ne nm nt or CP ? n 3 How much will Kamioka-Korea 2 detector setup (T 2 KK) contribute to these measurements?

Possible experimental setup 0. 27 Mton 2. 5 deg. off axis (or smaller off-axis Angle) 0. 27 Mton 2. 5 deg. off axis Distance from the target (km) JPARC 075 4 MW 2. 5 deg. off-axis beam @Kamioka Off-axis angle Fig. from Senda NP 04

Osc. probability in Kamioka and Korea sin 22 q 13=0. 05 BG & efficiency: almost identical both 2. 5 deg. off axis beam

Expected sensitivity hep-ph/0504026 Total mass of the detectors = 0. 54 Mton fid. mass 4 years neutrino beam + 4 years anti-neutrino beam Mass hierarchy 3 (thick) 2 (thin) CP violation (sind≠ 0)

Update (1) - 1050 km: a special baseline ? K. Okumura, 2 nd T 2 KK workshop, Seoul 2006 2. 5 degree off-axis beam with L between 1000 km and 1250 km is available. sin 22 q 13 Checked if the sensitivity depends strongly on the baseline length. Sensitivity to mass hierarchy (True = normal hierarchy) d The sensitivity does not depend strongly on L !

Update (2): higher energy option Motivation: Mass hierarchy ar. Xiv: 0705. 4396 3 (black) 3 (thick) T 2 KK ‘s sensitivity on mass hierarchy is still limited compared with the US studies… Higher energy better ?

Flux (arb. unit) Higher energy beam Energy Dependent Maximum Likelihood Analysis P(nm ne) 1. 0 to 2. 5 degree off axis beam available in Korea. En (Ge. V)

Signal and BG for various off-axis beams Korea Kamioka 2. 5 degree signal 1. 0 degree signal BG BG sin 2(2 q 13)=0. 1 d=1/2 p 4 year neutrino run 4 MW beam 2. 0 degree Smaller off-axis angle: Low E BG more serious. (2 nd osc. Max. difficult to see. ) But larger matter effect at the 1 st osc. Max. . 1. 5 degree 2. 5 degree

3 s sensitivities for various OA angles Mass hierarchy CP violation F. Dufour, 2 nd T 2 KK workshop, July 2006, Seoul (Updated) Pre lim 3 Kam only (OA 2. 5) Kam + Korea OA 1. 0 Kam + Korea OA 1. 5 Kam + Korea OA 2. 0 Kam + Korea OA 2. 5 Mass hierarchy: OA 1. 0 @Korea gives the best sensitivity CP violation: Sensitivity depends weekly on the beam option ina ry Could be slightly too optimistic for OA angle less than 2. 5 degrees (The syst errors are assumed to be fully correlated between 2 detectors)

Update (3): Octant ambiguity of q 23 In the previous study, maximal q 23 mixing (q 23=p/4) was assumed. However, q 23 might not be p/4. In this case, there should be additional ambiguity in the parameter measurements (especially in that of sin 2 q 13) due to the ambiguity in the octant of q 23 (i. e. , q 23 >45 or <45 deg. ). It will be very nice if the same setup can solve the octant ambiguity of q 23. Resolving 8 fold parameter degeneracy in T 2 KK

Oscillation probabilities and the signal P(nm ne) by the solar Dm 2 is proportional to sin 22 q 12 ・cos 2 q Atm. + CP terms 23 Solar oscillation effect visible in a very long baseline (or very large L/E) experiment. BG events Solar term sin 22 q 12・cos 2 q 23 effect visible ○sin 2 q 23 = 0. 4, sin 2 2 q 13 = 0. 01 ●sin 2 q 23 = 0. 6, sin 2 2 q 13 = 0. 0067 (sin 2 q 23・sin 22 q 13 is equal in the two cases. ) Dm 2: positive, d=p 3/4

Sensitivity to octant of q 23 OA 2. 5 degree for both Kamioka and Korea sin 22 q 13 sin 22 q 23=0. 96 sin 22 q 23=0. 99 hep-ph/0609286 2 3 Octant ambiguity of q 23 can be resolved at 2 if sin 22 q 23 < ~0. 97 (almost independent of the value of sin 22 q 13 and mass hierarchy). Could resolve the 8 hold degeneracy of the oscillation parameters.

Discussing T 2 KK more Sep. 30 and Oct. 1 Univ. of Tokyo Your participation and contribution are most welcome! http: //www-rccn. icrr. u-tokyo. ac. jp/workshop/T 2 KK 07/

• • If non-zero q 13 is observed…. We hope to proceed to the next phase of experiment with higher power beam and larger detector(s). Goals: discovery of leptonic CP violation, and determination of mass hierarchy and octant of q 23. (+ Various non-LBL physics). T 2 KK is one of the serious possibilities. We will continue the studies.

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