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Takaaki Kajita, ICRR, Univ. of Tokyo

TAUP07, Sep.2007, Sendai. Updating the future neutrino oscillation experiment With the Kamioka-Korea 2 detector setup. Takaaki Kajita, ICRR, Univ. of Tokyo. ◆Introduction ◆ T2KK @TAUP05 ◆Updating T2KK - L dependence, - Higher energy option, - Octant of q 23 , ◆Summary.

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Takaaki Kajita, ICRR, Univ. of Tokyo

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  1. TAUP07, Sep.2007, Sendai Updating the future neutrino oscillation experiment With the Kamioka-Korea 2 detector setup Takaaki Kajita, ICRR, Univ. of Tokyo ◆Introduction ◆T2KK @TAUP05 ◆Updating T2KK - L dependence,- Higher energy option, - Octant of q23, ◆Summary

  2. Introduction sin2q12, sin22q23, Dm122, |=Dm232|・・・・ Already measured. Let’s assume that non-zero q13 will be observed by the next generation oscillation experiments. 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 will Kamioka-Korea 2 detector setup (T2KK) contribute to these measurements?

  3. Detector in Korea ? T2KK @TAUP05

  4. Possible experimental setup 0.27Mton 0.27Mton 2.5 deg. off axis (or smaller off-axis Angle) 2.5 deg. off axis Distance from the target (km) JPARC 0754MW 2.5deg.off-axis beam @Kamioka Fig. from Senda NP04 Off-axis angle

  5. Osc. probability in Kamioka and Korea sin22q13=0.05 BG & efficiency: almost identical  both 2.5 deg. off axis beam

  6. 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 CP violation (sind≠0) 3 s (thick) 2 s (thin)

  7. Updating T2KK

  8. Update (1)- 1050km: a special baseline ? - K.Okumura, 2nd T2KK workshop, Seoul 2006 2.5 degree off-axis beam with L between 1000km and 1250km is available. Checked if the sensitivity depends strongly on the baseline length. sin22q13 Kam only L=1000km L=1050km Sensitivity to mass hierarchy (True = normal hierarchy) L=1100km L=1150km  The sensitivity does not depend strongly on L ! L=1200km L=1250km d 3s sensitivity

  9. Update (2): higher energy option Motivation: Mass hierarchy arXiv:0705.4396 3(black) 3 s (thick) T2KK ‘s sensitivity on mass hierarchy is still limited compared with the US studies…  Higher energy better ?

  10. Higher energy beam Flux (arb. unit) 1.0 to 2.5 degree off axis beam available in Korea. P(nmne) Energy Dependent Maximum Likelihood Analysis En (GeV)

  11. Signal and BG for various off-axis beams 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: Low E BG more serious. (2nd osc. Max. difficult to see.) But larger matter effect at the 1st osc. Max..

  12. 3s sensitivities for various OA angles F.Dufour, 2nd T2KK workshop, July 2006, Seoul (Updated) Mass hierarchy CP violation Preliminary 3 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) Kam only (OA2.5) Kam + Korea OA1.0 Kam + Korea OA1.5 Kam + Korea OA2.0 Kam + Korea OA2.5 Mass hierarchy: OA1.0 @Korea gives the best sensitivity CP violation: Sensitivity depends weekly on the beam option

  13. Update (3):Octant ambiguity of q23 In the previous study, maximal q23 mixing (q23=p/4) was assumed. However, q23 might not be p/4. In this case, there should be additional ambiguity in the parameter measurements (especially in that of sin2q13) due to the ambiguity in the octant of q23 (i.e., q23 >45 or <45 deg.). It will be very nice if the same setup can solve the octant ambiguity of q23. Resolving 8 fold parameter degeneracy in T2KK

  14. Oscillation probabilities and the signal P(nmne) by the solar Dm2 is proportional to sin22q12・cos2q23 Solar oscillation effect visible in a very long baseline (or very large L/E) experiment. sin22q12・cos2q23 effect visible Atm. + CP terms BG events Solar term ○sin2 q23= 0.4, sin2 2q13= 0.01 ●sin2 q23= 0.6, sin2 2q13= 0.0067 (sin2q23・sin22q13 is equal in the two cases.) Dm2: positive, d=p3/4

  15. sin22q13 Sensitivity to octant of q23 sin22q23=0.96 hep-ph/0609286 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). Could resolve the 8 hold degeneracy of the oscillation parameters.

  16. Discussing T2KK 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/T2KK07/

  17. Summary If non-zero q13 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 q23. (+ Various non-LBL physics). • T2KK is one of the serious possibilities. • We will continue the studies.

  18. End

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