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Osamu Yasuda

Publications and source records attributed to Osamu Yasuda.

At least 37 records · Page 2Linked to original sources
arXiv2014

The KTY formalism and nonadiabatic contributions to the neutrino oscillation probability

It is shown how to obtain the analytical expression for the effective mixing angle in matter using the formalism which was developed by Kimura, Takamura and Yokomakura. If the baseline of the neutrino path is long enough so that averaging over rapid oscillations is a good approximation, then with the help of Landau's method, the nonadiabatic contribution to the oscillation probability can be expressed analytically by this formalism. We give two examples in which the present method becomes useful.

hep-ph↗
arXiv2014

On nonadiabatic contributions to the neutrino oscillation probability and the formalism by Kimura, Takamura and Yokomakura

It is shown that it is possible to obtain the analytical expression for the effective mixing angle in matter using the formalism which was developed by Kimura, Takamura and Yokomakura for the neutrino oscillation probability in matter with constant density. If we assume that the imaginary part of the integral of the difference of the energy eigenvalues of the two levels at each level-crossing is given by the ratio $γ$ of the difference of the energy eigenvalues of the two levels to the derivative of the effective mixing angle at the level-crossing, then the nonadiabatic contribution to the oscillation probability can be expressed analytically by this formalism. We give one example in which the energy eigenvalues cannot be expressed as roots of a quadratic equation and we show that our assumption is correct in the approximation of the small mixing angle.

hep-ph↗
arXiv2013

Measurement of a Phase of a Radio Wave Reflected from Rock Salt and Ice Irradiated by an Electron Beam for Detection of Ultra-High-Energy Neutrinos

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE neutrino interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE neutrino shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE neutrino. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE neutrinos. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consistence with the power reflection fraction which was measured directly. A model taking into account the temperature change explained the phase and the amplitude of the reflected wave. Therefore the reflection mechanism was confirmed. The power reflection fraction was compared with that calculated with the Fresnel equations, the ratio between the measured result and that obtained with the Fresnel equations in ice was larger than that of rock salt.

astro-ph.IM↗
arXiv2011

Search for sterile neutrinos at reactors with a small core

The sensitivity to the sterile neutrino mixing at very short baseline reactor neutrino experiments is investigated. If the reactor core is relatively large as in the case of commercial reactors, then the sensitivity is lost for $Δm^2 \gtrsim$ 1 eV$^2$ due to smearing of the reactor core size. If the reactor core is small as in the case of the experimental fast neutron reactor Joyo, the ILL research reactor or the Osiris reactor, on the other hand, then sensitivity to $\sin^22θ_{14}$ can be as good as 0.03 for $Δm^2 \sim$ several eV$^2$ because of its small size.

hep-ph↗
arXiv2011

Search for sterile neutrinos at reactors

The sensitivity to the sterile neutrino mixing at very short baseline reactor neutrino experiments is investigated. In the case of conventional (thermal neutron) reactors it is found that the sensitivity is lost for $Δm^2 \gtrsim$ 1 eV$^2$ due to smearing of the reactor core size. On the other hand, in the case of an experimental fast neutron reactor Joyo, because of its small size, sensitivity to $\sin^22θ_{14}$ can be as good as 0.03 for $Δm^2 \sim$ several eV$^2$ with the Bugey-like detector setup.

hep-ph↗
arXiv2010

Some attempts to explain MINOS anomaly

Some attempts which were made to explain the MINOS anomaly are critically discussed. They include the non-standard neutral current-neutrino interaction and the (3+1)-scheme with sterile neutrino.

hep-ph↗
arXiv2010

Sensitivity of T2KK to non-standard interactions

Assuming only the non-zero electron and tau neutrino components $ε_{ee}$, $ε_{eτ}$, $ε_{ττ}$ of the non-standard matter effect and postulating the atmospheric neutrino constraint $ε_{ττ}=|ε_{eτ}|^2/(1+ε_{ee})$, the sensitivity to the non-standard interaction in neutrino propagation of the T2KK neutrino long-baseline experiment is estimated. It is found that T2KK can constrain the parameters $|ε_{ee}|\lesssim 1$, $|ε_{eτ}|\lesssim 0.2$.

hep-ph↗
arXiv2010

Some constraints on new physics by atmospheric neutrinos

From the analytic oscillation probability for high energy atmospheric neutrinos in the presence of new physics in propagation, it is argued that the components $|ε_{eμ}|$ and $|ε_{μτ}|$ as well as the quantity $|ε_{ττ}-|ε_{eτ}|^2/(1+ε_{ee})|$ should be small.

hep-ph↗
arXiv2010

Sensitivity of T2KK to the non-standard interaction in propagation

Assuming only the non-zero electron and tau neutrino components $ε_{ee}$, $ε_{eτ}$, $ε_{ττ}$ of the non-standard matter effect and postulating the atmospheric neutrino constraint $ε_{ττ}=|ε_{eτ}|^2/(1+ε_{ee})$, we study the sensitivity to the non-standard interaction in neutrino propagation of the T2KK neutrino long-baseline experiment. It is shown that T2KK can constrain the parameters $|ε_{ee}|\lesssim 1$, $|ε_{eτ}|\lesssim 0.2$. It is also shown that if $|ε_{eτ}|$ and $θ_{13}$ are large, then T2KK can determine the Dirac phase and the phase of $ε_{eτ}$ separately, due to the information at the two baselines. We also provide an argument that the components $|ε_{αμ}|$ $(α=e,μ,τ)$ must be small for the disappearance oscillation probability to be consistent with high-energy atmospheric neutrino data, which justifies our premise that these quantities are negligible.

hep-ph↗
arXiv2010

Summary report of MINSIS workshop in Madrid

Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard μ - τ flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal.

hep-ph↗
arXiv2010

Sensitivity to sterile neutrino mixings and the discovery channel at a neutrino factory

Sensitivity of a neutrino factory to various mixing angles in a scheme with one sterile neutrino is studied using $ν_e\toν_μ$, $ν_μ\toν_μ$, $ν_e\toν_τ$ and $ν_μ\toν_τ$. While the "discovery-channel" $ν_μ\toν_τ$ is neither useful in the standard three flavor scheme nor very powerful in the sensitivity study of sterile neutrino mixings, this channel is important to check unitarity and to probe the new CP phase in the scheme beyond the standard neutrino mixing framework.

hep-ph↗
arXiv2009

The discovery channel at the Neutrino Factory: $ν_μ\toν_τ$ pointing to sterile neutrinos

We study the potential of a Neutrino Factory in constraining the parameter space of a scheme with one sterile neutrino separated from three active ones by an O(1) eV^2, mass-squared difference. We present approximated analytic expressions for the oscillation probabilities, showing that the greatest sensitivity to sterile neutrinos at a Neutrino Factory can be achieved using the ν_μ->ν_μand the ν_μ->ν_τoscillations. We have studied two setups: a Neutrino Factory with 50 GeV (20 GeV) stored muons, with two detectors of the Hybrid-MIND type (a magnetized ECC next to a magnetized iron calorimeter), located at L=3000, 7500 km (L=4000, 7500 km) from the source. Four channels have been used: ν_e -> ν_μ,ν_τ; ν_μ-> ν_μ,ν_τ. The relevant backgrounds, efficiencies and systematic errors have been taken into account, and we have discussed dependence of the sensitivities on the systematic errors. We have found that the 50 GeV (20 GeV) setup can constrain \sin^2 2 θ^{(4fam)}_{13} <= 7x10^{-5} (2x10^{-4}); θ_{34} <= 12 deg (14 deg); and θ_{24}<= 7.5 deg (8 deg). Our results hold for any value of Δm^2_{Sbl} >~ 0.1 eV^2. Eventually we have shown that, if a positive signal is found, the proposed setup is able to measure simultaneously θ_{34} and δ_3 with a precision of few degrees and few tens of degrees, respectively, solving the so-called "intrinsic" and "sign degeneracies". Combination of ν_μdisappearance and of the ν_μ->ν_τchannel, that will be called "the discovery channel", at the two baselines is able to measure at 99% CL a new CP-violating phase δ_3 for \sin^2 2 θ_{34} >= 0.06.

hep-ph↗
arXiv2008

Signatures of sterile neutrino mixing in high-energy cosmic neutrino flux

Even after the negative result by the MiniBooNE experiment, we can still have a (3+1)-scheme with one sterile neutrino whose mixing lies within the allowed region by MiniBooNE. In this note we discuss the possible effects of such a scheme on the flavor ratio of high-energy cosmic neutrinos from cosmologically distant astrophysical sources. It is shown that in principle there is still a chance to observe deviation from the standard three flavor scenario in the flavor ratio of the high-energy cosmic neutrinos. It is proposed to see the energy spectrum to cope with the theoretical uncertainties which were recently pointed out by Lipari, Lusignoli and Meloni. It is emphasized that the $ν_μ-ν_τ$ ratio is relatively insensitive to the theoretical uncertainties and therefore this ratio is the key ingredient to look for the signatures of the sterile neutrino scheme. Although the statistics of data from one source in the next generation of neutrino telescopes are estimated not to be sufficient to distinguish the three and four family schemes, if we can gain statistics by, e.g., summing over data from many sources, then it might be possible to have a signature for the (3+1)-scheme.

hep-ph↗
arXiv2007

Physics and Performance Evaluation Group

We summarize the objectives and results of the ``international scoping study of a future neutrino factory and superbeam facility'' (ISS) physics working group. Furthermore, we discuss how the ISS study should develop into a neutrino factory design study (IDS-NF) from the point of view of physics and performance evaluation.

hep-ph↗
arXiv2007

Reflection of microwave from energy deposit by X-ray irradiation in rock salt: Implication of an ultra high energy salt neutrino detector to act like a radio bubble chamber

Existence of GZK neutrinos (ultra high energy neutrinos) have been justified although the flux is very low. A new method is desired to use a huge mass of a detector medium to detect them. A fundamental study of radar method was carried out to measure microwave reflection from electromagnetic energy deposit by X-ray irradiation in a small rock salt sample. The reflection rate of 1x10^-6 was found at the energy deposit of 1x10^19 eV which was proportional to square of the X-ray intensity suggesting the effect to be coherent scattering. The decay time of the reflection was several seconds. This effect implies a large scale natural rock salt formation could be utilized like a bubble chamber irradiated by radio wave instead of visible light to detect GZK neutrinos.

astro-ph↗
arXiv2007

New Physics Effects in Long Baseline Experiments

We discuss the implications of new physics, which modifies the matter effect in neutrino oscillations, to long baseline experiments, particularly the MINOS experiment. An analytic formula in the presence of such a new physics interaction is derived for $P(ν_μ\toν_e)$, which is exact in the limit $Δm^2_{21}\to0$.

hep-ph↗
arXiv2007

On the exact formula for neutrino oscillation probability by Kimura, Takamura and Yokomakura

The exact formula for the neutrino oscillation probability in matter with constant density, which was discovered by Kimura, Takamura and Yokomakura, has been applied mostly to the standard case with three flavor neutrino so far. In this paper applications of their formula to more general cases are discussed. It is shown that this formalism can be generalized to various cases where the matter potential have off-diagonal components, and the two non-trivial examples are given: the case with magnetic moments and a magnetic field and the case with non-standard interactions. It is pointed out that their formalism can be applied also to the case in the long baseline limit with matter whose density varies adiabatically as in the case of solar neutrino.

hep-ph↗