Mayumi Aoki

Contributions of vector-like quarks to radiative B meson decay

Abstract We study the decay B → X s γ in a minimal extension of the standard model with extra up- and down-type quarks whose left- and right-handed components are both SU(2) singlets. Constraints on the extended Cabibbo–Kobayashi–Maskawa matrix are obtained from the experimental results for the branching ratio. Even if the extra quarks are too heavy to be detected in near-future colliders, the branching ratio could have a value which is non-trivially different from the prediction of the standard model.

Lifting degeneracies in the oscillation parameters by a neutrino factory

Abstract We study the potential of a very long baseline neutrino oscillation experiment with a neutrino factory and a large segmented water-Cerenkov calorimeter detector in resolving the degeneracies in the neutrino oscillation parameters; the sign of the larger mass-squared difference δ m 13 2 , the sign of | U μ 3 | 2 ( ≡ sin 2 θ ATM ) − 1 / 2 , and a possible two-fold ambiguity in the determination of the CP phase δ MNS . We find that the above problems can be resolved even if the particle charges are not measured. The following results are obtained in our exploratory study for a neutrino factory which delivers 10 21 decaying μ + and μ − at 10 GeV and a 100 kton detector which is placed 2100 km away and is capable of measuring the event energy and distinguishing e ± from μ ± , but not their charges. The sign of δ m 13 2 can be determined for 4 | U e 3 | 2 ( 1 − | U e 3 | 2 ) ≡ sin 2 2 θ RCT ≳ 0.008 . That of sin 2 θ ATM − 1 / 2 can be resolved for sin 2 2 θ ATM = 0.96 when sin 2 2 θ RCT ≳ 0.06 . The CP-violating phase δ MNS can be uniquely constrained for sin 2 2 θ RCT ≳ 0.02 if its true value is around 90° or 270°, while it can be constrained for sin 2 2 θ RCT ≳ 0.03 if its true value is around 0° or 180°.

Physics potential of future long baseline neutrino oscillation experiments with KEK-JAERI HIPA

Abstract We study physics potential of Very Long Base-Line (VLBL) Neutrino-Oscillation Experiments with the High Intensity Proton Accelerator, which will be completed by the year 2007 in Tokai-village, Japan. As a target, a 100 kton-level water-Cerenkov detector is considered at 2,100 km away. Assuming the pulsed narrow-band ν μ beams, we study sensitivity of such experiments to the neutrino mass hierarchy, the mass-squared differences, one CP phase and three angles of the lepton-flavor-mixing matrix. We find that experiments at a distance 2,100 km can determine the neutrino mass hierarchy if the mixing matrix element | U e3 | is not too small. The CP phase and | U e3 | can be constrained if the large-mixing-angle solution of the solar-neutrino deficit is realized.

Large effects on B s B s mixing by vectorlike quarks

We calculate the contributions of the vector-like quark model to

Tau polarization effects in the CNGS ντ appearance experiments

\BsBs

The decay of tau leptons produced in neutrino–nucleon scatterings

mixing, taking into account the constraints from the decay

Semi-leptonic and rare decays

B\to X_s\gamma

Decay rate asymmetry for B→Xsγ in the SUSY model

. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However,

Decay rate asymmetry for

\BsBs

B \to X_s \gamma

mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In sizable ranges of the model parameters, the mixing parameter