Joe Sato

Large lepton mixing in a coset-space family unification on E7/SU(5)×U(1)3

Abstract We study a coset-space unification model for families based on E 7 /SU(5)×U(1) 3 . We find that qualitative structure of quark and lepton mass matrices in this model describes very well the observation. We stress, in particular, that the large mixing angle, sin 2 2 θ ν μ ν τ ≃1, required for the atmospheric neutrino oscillation reported by the SuperKamiokande collaboration, is naturally obtained, which is a consequence of unparallel family structure in the present coset-space unification.

CP and T violation tests in neutrino oscillation

We examine how large violation effects of CP and T are allowed in long baseline neutrino experiments. When we attribute only the atmospheric neutrino anomaly to neutrino oscillation we may have large CP-violation effects. When we attribute both the atmospheric neutrino anomaly and the solar neutrino deficit to neutrino oscillation we may have sizable T violation effects proportional to the ratio of the two mass differences; it is difficult to see CP violation since we cannot ignore the matter effect. We give a simple expression for T violation in the presence of matter. {copyright} {ital 1997} {ital The American Physical Society}

Oscillation-enhanced search for new interaction with neutrinos

We discuss the measurement of new physics in long baseline neutrino oscillation experiments. Through neutrino oscillations, the probability to detect new physics effects such as flavor violation is enhanced by interference with the weak interaction. We carefully explain the situations in which interference can take place. Assuming a neutrino factory and an upgraded conventional beam, we estimate the feasibility to observe new physics numerically and point out that we can search new interactions using some channels, for example,

A Constraint on Yukawa-Coupling Unification from Lepton-Flavor Violating Processes

{\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}},

Neutrino oscillation and CP violation

in these experiments. We also discuss several models which induce effective interactions interfering with the weak interaction, and show that some new physics effects are large enough to be observed in an oscillation enhanced way.

Long life stau in the minimal supersymmetric standard model

We present a new constraint on a lepton mixing matrix V from lepton-flavor violating (LFV) processes in supersymmetric standard models with massive neutrinos. Here, we assume Yukawa-coupling unification f�3 ≃ ftop, in which �-neutrino Yukawa coupling f�3 is unified into top-quark Yukawa coupling ftop at the unification scale M� ≃ 3 × 10 16 GeV. We show that the present experimental bound on µ → e decay already gives a stringent limit on the lepton mixing (typically V13 < 0.02 for V23 = 1/ √ 2). Therefore, many existing neutrino-mass models are strongly constrained. Future improvement of bounds on LFV processes will provide a more significant impact on the models with the Yukawa-coupling unification. We also stress that a precise measurement of a neutrino mixing (VMNS)e3 in future neutrino experiments would be very important, since the observation of non-zero (VMNS)e3, together with negative experimental results for the LFV processes, have a robust potential to exclude a large class of SUSY standard models with the Yukawa-coupling unification.

Can ICARUS and OPERA ντ appearance experiments detect new flavor physics

We reconsider the meaning of observing CP violation in neutrino oscillation.

Low-energy predictions of lopsided family charges

We study the stau lifetime in a scenario with the LSP taken to be a neutralino and the NLSP being a stau, based on the minimal supersymmetric Standard Model. The mass difference between the LSP and NLSP, {delta}m, must satisfy {delta}m/m{sub {chi}}{sub -tilde}{approx} a few % or less for coannihilation to occur, where m{sub {chi}}{sub -tilde} is the neutralino mass. We calculate the stau lifetime from the decay modes {tau}-tilde{yields}{chi}-tilde{tau}, {chi}-tilde{nu}{sub {tau}}{pi}, and {chi}-tilde{nu}{sub {tau}}{mu}(e){nu}{sub {mu}}{sub (e)} and discuss its dependence on various parameters. We find that the lifetime is in the range 10{sup -22}-10{sup 16} sec for 10{sup -2}{<=}{delta}m{<=}10 GeV. We also discuss the connection with lepton flavor violation if there is mixing between sleptons.

MONOENERGETIC NEUTRINO BEAM FOR LONG BASELINE EXPERIMENTS

Abstract In this Letter we explore the notion of whether it is possible to observe a flavor-changing effect in the τ appearance experiments, ICARUS and OPERA.

Possible solution to the 7Li problem by the long lived stau

We consider the Froggatt-Nielsen (FN) mechanism reproducing the observed mass hierarchies and mixing angles for quarks and leptons. The large