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Takaaki Kajita ICRR, Univ. of Tokyo Work done with S.Nakayama, Y.Obayashi, K.Okumura, M.Shiozawa

NNN05 workshop, Aussois, Savoie, France, April 2005. Neutrino oscillation studies with atmospheric neutrinos in Hyper-Kamiokande. Takaaki Kajita ICRR, Univ. of Tokyo Work done with S.Nakayama, Y.Obayashi, K.Okumura, M.Shiozawa. - sub-dominant osc. in atm. neutrino exp's -. Introduction.

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Takaaki Kajita ICRR, Univ. of Tokyo Work done with S.Nakayama, Y.Obayashi, K.Okumura, M.Shiozawa

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  1. NNN05 workshop, Aussois, Savoie, France, April 2005 Neutrino oscillation studies with atmospheric neutrinos in Hyper-Kamiokande Takaaki Kajita ICRR, Univ. of Tokyo Work done with S.Nakayama, Y.Obayashi, K.Okumura, M.Shiozawa - sub-dominant osc. in atm. neutrino exp's -

  2. Introduction • mass and mixing parameters: q12, q23, q13, d, Dm122, Dm132(=Dm232) Known: Unknown: q12, Dm122 q23, |Dm232| q13 Sign of Dm232 nenmnt n3 or n2 n1 If q23 ≠p/4, is it >p/4 or <p/4 ? CP ? Solar, KamLAND Atmospheric Long baseline How much can we learn from atmospheric neutrino experiments?

  3. Outline • Introduction • sin2q13 ? • Sign of Dm232 ? • . q23 >p/4 or <p/4 ? (including solar oscillation terms) • CP phase measurement ? • Summary

  4. Detector and assumption Detector: Hyper-Kamiokande The performance of the Hyper-K detector is assumed to be identical to Super-K. Fiducial mass = 0.54 Mton 54m 48m 250m

  5. Search for non-zero q13 (Dm122=0 assumed) 0.45 Mtonyr Matter effect 1+multi-ring, e-like, 2.5 - 5 GeV Electron appearance cosqzenith s213=0.05 s213=0.00 null oscillation En(GeV) cosqzenith Electron appearance in the multi-GeV upward going events.

  6. Binning for this analysis (= 3flavor analysis in SK) 10 zenith angle bins for each box. Sub-GeV Multi-GeV Up-stop Single-Ring m Multi-Ring m PC- stop Single-Ring e Multi-Ring e PC- through Up-through En CC ne CC nm 37 momentum bins x 10 zenith bins = 370 bins in total (or slightly smaller number of bins for some analyses) Small number of events per bin Poisson statistics to claculate c2 with 44 systematic error terms

  7. Importance of s2q23>0.5; S.Pascoli et al., hep-ph/0305152 Statistical significance for non-zero q13 450 kton・yr = 0.8yr HKDm232 ; positive assumed 3s 3s 3s (Dc2 is approximately proportional to the exposure)

  8. Sign of Dm2 ? Dm2=0.002eV2 s2q23 = 0.5 s2q13 = 0.05 (0.45 Mtonyr) If Dm232 is positive, resonance for neutrinos If Dm232 is negative, resonance for anti-neutrinos Single-ring e-like Multi-ring e-like Relatively high anti-ne fraction Relatively high ne fraction Positive Dm2 Negative Dm2 null oscillation cosQ cosQ

  9. c2 difference (inverted-normal) True= normal mass hierarchy assumed. Dm2: fixed, q23: free, q13: free Exposure: 1.8Mtonyr (HK = 3.3 yr) 3s 3s 3s

  10. c2 difference (normal – inverted) True= inverted mass hierarchy assumed. Dm2: fixed, q23: free, q13: free Exposure: 1.8Mtonyr (HK =3.3 yr) 3s 3s 3s

  11. q23 >p/4 or <p/4 ? CP phase measurement ?

  12. However, due to the cancellation between nmne and nenm, the change in the ne flux is small. s2q23=0.4 =0.6 =0.5 Oscillation probability is different between s2q23=0.4 and 0.6  discrimination between q23 >p/4 and <p/4 might be possible. Peres & Smirnov NPB 680 (2004) 479 Expected oscillation with solar terms (1) Because of the LMA solution, atmospheric neutrinos should also oscillate by (q12, Dm122). s22q12=0.825 Dm212=8.3×10-5 Dm223=2.5×10-3 sin2q13=0

  13. s2q23=0.4 s2q13=0.0 s2q23=0.4 s2q13=0.04 dcp=p/4 Effect of LMA Effect of q13 Interference (CP) Expected oscillation with solar terms (2) s22q12=0.825 Dm212=8.3×10-5 Dm223=2.5×10-3 (always assumed later in this talk) In addition, we may have non-zero q13.

  14. Effect of the solar term to sub-GeV e-like zenith angle Dm212 = 8.3 x 10-5 eV2 Dm223 = 2.5 x 10-3 eV2 sin2 2q12 = 0.82 sin2q13=0 sub-GeV e-like (Pe :100 ~ 1330 MeV) (Pe :100 ~ 400 MeV) (Pe :400 ~ 1330 MeV) sin2 q23 = 0.4 sin2 q23 = 0.5 sin2 q23 = 0.6 e-like (3 flavor) / e-like (2 flavor full-mixing) cosqzenith (Much smaller and opposite effect for m-like events.) m/e ratio @low energy is useful to discriminate q23>p/4 and <p/4.

  15. Discrimination between q23 >p/4 and <p/4 with the (12) and (13) terms s2q23=0.40 ~ 0.60 s2q13=0.00~0.04 dcp=45o 1.8Mtonyr = 3.3 yrs HK 90%CL 90%CL sin22q23=0.96 sin22q23=0.99 Fit result Test point sin2q13 sin2q23 sin2q23 Discrimination between q23>p/4 and <p/4 is possible for all q13. Discrimination between q23>p/4 and <p/4 is marginally possible only for q13 >0.04.

  16. Effect of dCP in atmospheric neutrino data no osc. with 80yrs stat.error dCP=45o 135o 225o 315o s22q12=0.825 s2q23=0.5 s2q13=0.04 Dm212=+8.3e-5 Dm223=+2.5e-3 Mutli-GeV, multi-ring e-like CP effect e-like (3 flavor) / e-like (no-osc) q13 effect cosqzenith

  17. s22q12=0.825 s2q23=0.5 s2q13=0.01~0.04 Dm212=+8.3e-5 Dm223=+2.5e-3 Sensitivity to dcp 1.8 Mtonyr ~ 3.3yrs HK sin2q13=0.04 Test (d,q13) point 99%CL 90%CL 0.1 0 sin2q13=0.02 sin2q13 0.1 0 0.1 sin2q13=0.01 0 0 p 2p 0 p 2p 0 p 2p 0 p 2p CP phase d CP phase could be seen if q13 is close to the CHOOZ limit.

  18. Summary • The present Monte Carlo study suggests that the future atmospheric neutrino experiments with very high statistics will be very interesting, if q13 is large enough. • For large q13, atmospheric neutrino experiments with > 2 Mtonyr exposure will; discriminate the mass hierarchy discriminate between q23 >p/4 and <p/4 (if sin22q23 is smaller than 0.99) (if sin22q23 is about 0.96 or smaller, the discrimination is possible even if q13=0) give some information on the CP phase

  19. End

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