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Osamu Yasuda

Publications and source records attributed to Osamu Yasuda.

At least 55 records · Page 3Linked to original sources
arXiv2006

Will MINOS see new physics?

The effect of non-standard neutrino interactions with matter at long baseline neutrino experiments is examined in a model independent way, taking into account the constraints from all the experiments. It is found that such a non-standard interaction can enhance the flavor transition probability so significantly that the ongoing experiment MINOS may see the signal of $ν_μ\toν_e$ which is much more than the prediction by the standard scenario. It is also found that the silver channel $ν_e\toν_τ$ at a neutrino factory could have a huge enhancement.

hep-ph↗
arXiv2004

Parameter degeneracies and new plots in neutrino oscillations

It is shown that plots of constant probabilities in the $(\sin^22θ_{13}, 1/s^2_{23})$ plane enable us to see eightfold degeneracy easily. Using this plot, I discuss how an additional long baseline measurement resolves degeneracies after the JPARC experiment measures the oscillation probabilities $P(ν_μ\toν_e)$ and $P(\barν_μ\to\barν_e)$ at $|Δm^2_{31}|L/4E=π/2$.

hep-ph↗
arXiv2004

Degeneracy and strategies of long baseline and reactor experiments

Assuming that the JPARC experiment measures the oscillation probabilities $P(ν_μ\toν_e)$ and $P(\barν_μ\to\barν_e)$ at $|Δm^2_{31}|L/4E=π/2$, I discuss what kind of extra experiment (long baseline or reactor) can contribute to determination of $θ_{13}$ and the CP phase $δ$.

hep-ph↗
arXiv2004

Towards exploring $U_{e3}$

It is emphasized that resolution of the $θ_{23}$ ambiguity is important for determination of $θ_{13}$ if $\sin^22θ_{23}<1$, and resolution of the sgn($Δm^2_{31}$) ambiguity is important for determination of the CP phase $δ$. I discuss the prospects of resolution of the $θ_{23}$ ambiguity etc. in the future long baseline experiment after the JPARC experiment measures the oscillation probabilities $P(ν_μ\toν_e)$ and $P(\barν_μ\to\barν_e)$ at $|Δm^2_{31}|L/4E=π/2$.

hep-ph↗
arXiv2004

New plots and parameter degeneracies in neutrino oscillations

It is shown that eightfold degeneracy in neutrino oscillations is easily seen by plotting constant probabilities in the $(\sin^22θ_{13}, 1/s^2_{23})$ plane. Using this plot, we discuss how an additional long baseline measurement resolves degeneracies after the JPARC experiment measures the oscillation probabilities $P(ν_μ\toν_e)$ and $P(\barν_μ\to\barν_e)$ at $|Δm^2_{31}|L/4E=π/2$. By measuring $P(ν_μ\toν_e)$ or $P(\barν_μ\to\barν_e)$, the sgn($Δm_{31}^2$) ambiguity is resolved better at longer baselines and the $δ\leftrightarrowπ-δ$ ambiguity is resolved better when $||Δm^2_{31}|L/4E-π/2|$ is larger. The $θ_{23}$ ambiguity may be resolved as a byproduct if $||Δm^2_{31}|L/4E-π|$ is small and the CP phase $δ$ turns out to satisfy $|\cos(δ+|Δm^2_{31}|L/4E)|\sim1$. It is pointed out that the low energy option ($E\sim$1GeV) at the off-axis NuMI experiment may be useful in resolving these ambiguities. The $ν_e\toν_τ$ channel offers a promising possibility which may potentially resolve all the ambiguities.

hep-ph↗
arXiv2004

Measurement of $\sin^2{2θ_{13}}$ by reactor experiments and its sensitivity

Reactor experiments offer a promising way to determine $θ_{13}$ and are free from parameter degeneracies in neutrino oscillations. It is described how reactor measurements of $\sin^22θ_{13}$ can be improved by a near-far detector complex. The experimental lower bound is derived on the sensitivity to $\sin^2{2θ_{13}}\gtrsim 0.02$ based on the rate analysis, and an idea is given which may enable us to circumvent this bound. It is shown that in the Kashiwazaki-Kariwa plan (KASKA) the sensitivity to $\sin^2{2θ_{13}}$ is approximately 0.02.

hep-ph↗
arXiv2003

Measurement of $θ_{13}$ by reactor experiments

I describe how reactor measurements of $\sin^22θ_{13}$ can be improved by a near-far detector complex. I show that in the Kashiwazaki plan it is potentially possible to measure $\sin^2{2θ_{13}}$ down to 0.02.

hep-ph↗
arXiv2003

Parameter degeneracy and reactor experiments

Degeneracies of the neutrino oscillation parameters are explained using the $\sin^22θ_{13}$--$s^2_{23}$ plane. Measurements of $\sin^22θ_{13}$ by reactor experiments are free from the parameter degeneracies which occur in accelerator appearance experiments, and reactor experiments play a role complementary to accelerator experiments. It is shown that the reactor measurement may be able to resolve the degeneracy in $θ_{23}$ if $\sin^22θ_{13}$ and $\cos^22θ_{23}$ are relatively large.

hep-ph↗
arXiv2003

Summary of Working Group 2

Issues on the physics of, beamlines for, and detectors of neutrino oscillation discussed in Working Group 2 at Nufact'02 are summarized.

hep-ph↗
arXiv2001

Summary of Working Group 1: Theory Part

I will summarize theoretical issues in Working Group 1 at Nufact'01. Although there may not be complete agreement yet on the exact optimum baseline $L$ and the muon energy $E_μ$ for measurements of the CP phase at a neutrino factory, all the works done so far indicate that the optimum set ($L$, $E_μ$) tends to be smaller than (3000km, 50GeV) if the uncertainty of the matter effect is assumed to be larger than $\pm$5% or the background fraction is much larger than $10^{-5}$.

hep-ph↗
arXiv2001

Recent Status of Neutrino Oscillation Study

I review briefly the recent status of research on neutrino oscillations, such as three and four flavor analysis of atmospheric neutrinos and solar neutrinos, and prospects of present and future long baseline experiments.

hep-ph↗
arXiv2001

Vacuum mimicking phenomena in neutrino oscillations

It is shown generally that any oscillation probability in matter with approximately constant density coincides with that in vacuum to the first two nontrivial orders in $Δm^2_{jk}L/E$ if $|Δm^2_{jk}L/E|\ll 1$ and $|G_F N_e L|\ll 1$ are satisfied.

hep-ph↗
arXiv2001

Correlations of errors in measurements of CP violation at neutrino factories

Using $Δχ^2$ which is defined by the difference of the number of events with the CP phase $δ$ and the hypothetical one with $δ=0$, we discuss correlations of errors of the CP phase and other oscillation parameters as well as the matter effect in measurements at neutrino factories. By varying the oscillation parameters and the normalization of the matter effect, we evaluated the data size required to reject a hypothesis with $δ=0$ at 3$σ$CL. The optimum muon energy and the baseline depends on the magnitude of $θ_{13}$, the background fraction, the uncertainty of the normalization of the matter effect, but in general lie in the ranges 20GeV $\lesssim E_μ\lesssim$ 50GeV, 1000km$\lesssim L\lesssim$3000km. If we assume that the uncertainty of the matter effect is as large as 20% then the optimum values may be modified to $E_μ\lesssim$ 10GeV, $L\lesssim$1000km due to the strong correlation of $δ$ and the matter effect. We show analytically that sensitivity to CP violation is lost for $E_μ\ll$ 10GeV or for $E_μ\gg$ 50GeV. We also discuss the possibility of measuring CP violation at the upgraded JHF experiment by taking all the error correlations into account, and show that it is possible to demonstrate $δ\ne0$ at 3$σ$CL for $θ_{13}\gtrsim 3^\circ$.

hep-ph↗
arXiv2001

Neutrino Oscillations with Four Generations

Recent status of neutrino oscillation phenomenology with four neutrinos is reviewed. It is emphasized that the so-called (2+2)-scheme as well as the (3+1)-scheme are still consistent with the recent solar and atmospheric neutrino data.

hep-ph↗
arXiv2001

Various Solutions of the Atmospheric Neutrino Data

Various solutions of the atmospheric neutrino data are reviewed. Apart from orthodox two flavor $ν_μ\leftrightarrowν_τ$ oscillations and three flavor oscillations, there are still possibilities, such as four flavor oscillations with the (2+2)- and (3+1)- schemes, a neutrino decay scenario and decoherence, which give a good fit to the data.

hep-ph↗