arXiv subjects

Hidekazu Yokomakura

Publications and source records attributed to Hidekazu Yokomakura.

5 recordsLinked to original sources

arXiv2011

Supernova neutrino signals by liquid Argon detector and neutrino magnetic moment

We study electron-neutrino and electron-antineutrino signals from a supernova with strong magnetic field detected by a 100 kton liquid Ar detector. The change of neutrino flavors by resonant spin-flavor conversions, matter effects, and neutrino self-interactions are taken into account. Different neutrino signals, characterized by neutronization burst event and the total event numbers of electron-neutrinos and electron-antineutrinos, are expected with different neutrino oscillation parameters and neutrino magnetic moment. Observations of supernova neutrino signals by a 100 kton liquid Ar detector would constrain oscillation parameters as well as neutrino magnetic moment in either normal and inverted mass hierarchies.

astro-ph.HE↗

arXiv2005

Enhancement of CP Violating terms for Neutrino Oscillation in Earth Matter

We investigate the $ν_e \to ν_μ$ oscillation in the framework of three generations when neutrinos pass through the earth. The oscillation probability is represented by the form, $P(ν_e \to ν_μ)=A\cos δ+B\sin δ+C$ in arbitrary matter profile by using the leptonic CP phase $δ$. We compare our approximate formula in the previous paper with the formula which includes second order terms of $α=Δm_{21}^2/Δm_{31}^2$ and $s_{13}=\sin θ_{13}$. Non-perturbative effects of $α$ and $s_{13}$ can be taken into account in our formula and the precision of the formula is rather improved around the MSW resonance region. Furthermore, we compare the earth matter effect of $A$ and $B$ with that of $C$ studied by other authors. We show that the magnitude of $A$ and $B$ can reach a few ten % of $C$ around the main three peaks of $C$ in the region $E>1$ GeV by numerical calculation. We give the qualitative understanding of this result by using our approximate formula. The mantle-core effect, which is different from the usual MSW effect, appears not only in $C$ but also in $A$ and $B$, although the effect is weakened.

hep-ph↗

arXiv2004

Proposal of a Simple Method to Estimate Neutrino Oscillation Probability and CP Violation in Matter

We study neutrino oscillation within the framework of three generations in matter. We propose a simple method to approximate the coefficients A, B and C which do not depend on the CP phase δin the oscillation probability P(ν_e \to ν_μ)=A\cos δ+ B\sin δ+C. An advantage of our method is that an approximate formula of the coefficients A, B and C in arbitrary matter {\it without the usual first order perturbative calculations} of the small parameter Δm_{21}^2/Δm_{31}^2 or \sin θ_{13} can be derived. Furthermore we show that all the approximate formulas for low, intermediate and high energy regions given by other authors in constant matter can be easily derived from our formula. It means that our formula is applicable over a wide energy region.

hep-ph↗

arXiv2002

Exact Formulas and Simple CP dependence of Neutrino Oscillation Probabilities in Matter with Constant Density

We investigate neutrino oscillations in constant matter within the context of the standard three neutrino scenario. We derive an exact and simple formula for the oscillation probability applicable to all channels. In the standard parametrization, the probability for $ν_e$ $\to$ $ν_μ$ transition can be written in the form $P(ν_e \to ν_μ)=A_{eμ}\cosδ+B_{eμ}\sinδ+C_{eμ}$ without any approximation using CP phase $δ$. For $ν_μ$ $\to$ $ν_τ$ transition, the linear term of $\cos 2δ$ is added and the probability can be written in the form $P(ν_μ \to ν_τ)=A_{μτ}\cosδ+B_{μτ} \sinδ+C_{μτ}+D_{μτ}\cos 2δ$. We give the CP dependences of the probability for other channels. We show that the probability for each channel in matter has the same form with respect to $δ$ as in vacuum. It means that matter effects just modify the coefficients $A$, $B$, $C$ and $D$. We also give the exact expression of the coefficients for each channel. Furthermore, we show that our results with respect to CP dependences are reproduced from the effective mixing angles and the effective CP phase calculated by Zaglauer and Schwarzer. Through the calculation, a new identity is obtained by dividing the Naumov-Harrison-Scott identity by the Toshev identity.

hep-ph↗

arXiv2002

Overall Feature of CP dependence for Neutrino Oscillation Probability in Arbitrary Matter Profile

We study the CP dependence of neutrino oscillation probability for all channels in arbitrary matter profile within three generations. We show that an oscillation probability for ν_e \to ν_μcan be written in the form P(ν_e \to ν_μ) =A_{eμ} cos δ+ B_{eμ} sin δ+ C_{eμ} without any approximation using the CP phase δ. This result holds not only in constant matter but also in arbitrary matter. Another probability for ν_μ\to ν_τcan be written in the form P(ν_μ\to ν_τ)= A_{μτ} cos δ+ B_{μτ} sin δ + C_{μτ} + D_{μτ} cos 2δ+ E_{μτ} sin 2δ. The term which is proportional to sin 2δdisappear, namely E_{μτ}=0, in symmetric matter. It means that the probability reduces to the same form as in constant matter. As for other channels, probabilities in arbitrary matter are at most the quadratic polynomials of sin δand cos δas in the above two channels. In symmetric matter, the oscillation probability for each channel reduces to the same form with respect to δas that in constant matter.

hep-ph↗