arXiv subjects

T. Hasuike

Publications and source records attributed to T. Hasuike.

5 recordsLinked to original sources

arXiv2003

Flavor changing neutrino interactions and CP violation in neutrino oscillations

We investigate the interference effects of non-standard neutrino-matter interactions (NSNI) with the mass-induced neutrino oscillations. The NSNI is composed of flavor-changing neutrino interactions (FCNI) and flavor-diagonal neutrino interactions (FDNI). Both of the interactions are introduced in the ν_μ-ν_τsector and the ν_e -ν_μsector in order to study their effects in ν_μ\toν_τand ν_μ\toν_e oscillations, respectively. The FCNI effect proves to possibly dominate the CP violating effect and significantly survive as a fake CP violating effct in the neutrino energy region where the pure CP violating effect, ordinary matter effect and FDNI effect fall, for example, above 4 GeV at the baseline of L=730 km in the ν_μ\toν_τoscillation for the maximum parameter values of FCNI and FDNI allowed by the atmospheric neutrino oscillation data. The FCNI and FDNI effects on CP violation in the $ν_μ\toν_e$ oscillation are negligibly small due to the stringent constraints on FCNI from the bounds on lepton flavor violating processes and on FDNI from the limits on lepton universality violation.

hep-ph↗

arXiv2001

CP violation and matter effect in long-baseline neutrino oscillation in the four-neutrino model

We investigate the CP violation effect and the matter effect in the long-baseline neutrino oscillations in the four-neutrino model with mass scheme of the two pairs of two close masses separated by a gap of the order of 1 eV by using the constraints on the mixing matrix derived from the solar neutrino deficit, atmospheric neutrino anomaly, LSND experiments, and the other terrestrial neutrino oscillation experiments. We also use the results of the combined analyses by Gonzalez-Garcia, Maltoni, and Peña-Garay of the solutions to the solar and atmospheric neutrino problems with the recent SNO solar neutrino data. For the solution of close-to-active solar neutrino oscillations plus close-to-sterile atmospheric neutrino oscillations, the pure CP violation part of the oscillation probability difference between the CP-conjugate channels could attain as large as $0.10-0.25$ in the neutrino energy range of $E = 6-15$ GeV at the baseline $L = 730$ km for $ν_μ\toν_τ$ oscillation, and the matter effect is at the $8-15%$ level of the pure CP violation effect, while for the solution of near-pure-sterile solar neutrino oscillations plus near-pure-active atmospheric neutrino oscillations, the pure CP violation effect in $ΔP(ν_μ\toν_τ)$ is very small $(\sim 0.01)$ and is comparable to the matter effect. For $ν_μ\toν_e$ oscillation, the pure CP violation effect is independent of the active-sterile admixture and is at most 0.05 in $E = 1.5-3$ GeV at $L = 290$ km and the matter effect is at the $15-30%$ level.

hep-ph↗

arXiv2000

Four-neutrino model and the K2K experiment

We investigate the neutrino oscillations of ν_μbeam at the K2K experiment in the four-neutrino model with three active and one sterile neutrinos, and compare them with the oscillations in the three-neutrino model. In the four-neutrino case, the effect of the Δm^2_{LSND} scale of mass-squared difference, derived from the LSND experiments, occurs in the survival probability P(ν_μ\to ν_μ) in the range of Δm^2 < 0.004 eV^2, where Δm^2 is the relevant one to the K2K experiment and corresponds to the atmospheric neutrino mass scale. Once the probability P(ν_μ\to ν_μ) is measured at the K2K, the allowed region of Δm^2 would turn out to be broader in the four-neutrino model than the one in the three-neutrino model.

hep-ph↗

arXiv1999

Effects of the $K^+\toπ^+ν\barν$ and of other processes on the mixing hierarchies in the four-generation model

We analyze in the four-generation model the first measurement of the branching ratio of rare kaon decay $K^+\toπ^+ν\bar{nu}$, along with the other processes of $K_L-K_S$ mass difference $Δm_K$, CP-violating parameter $ε_K, B_d-\bar{B_d}$ mixing, $B_s-\bar{B_s}$ mixing, $B(K_L\toμ\barμ)$, and the upper bound values of $D^0-\bar{D^0}$ mixing and $B(K_L\toπ^0ν\barν)$, and try to search for mixing of the fourth generation in the hierarchical mixing scheme of the Wolfenstein parametrization. Using the results for the mixing of the fourth generation, we discuss predictions of the $D^0-\bar{D^0}$ mixing ($Δm_D$) and the branching ratio of directly CP-violating decay process $K_L\toπ^0ν\barν$, and the effects on the CP asymmetry in neutral B meson decays and the unitarity triangle.

hep-ph↗

arXiv1998

K^+\toπ^+ν\barν with four generations and its effects on unitarity triangle

We analyze in the four-generation model the first measurement of the branching ratio of rare kaon decay K^+\toπ^+ν\barν, using the constraints from Δm_K, ε_K, B_d-\bar{B_d} mixing, Γ(b\to sγ), B_s-\bar{B_s} mixing, D^0-\bar{D^0} mixing, B(K_L\toπ^0ν\barν) and B(K_L\toμ\barμ), and study its effects on the unitarity triangle. With the results of searching for the maximum mixing of the fourth generation, we predict that D^0-\bar{D^0} mixing Δm_D and the branching ratio of "direct" CP-violating decay process K_L\toπ^0ν\barν could attain the values 1-2 orders of magnitude larger than the predictions of the Standard Model.

hep-ph↗