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Joe Sato

Publications and source records attributed to Joe Sato.

At least 91 records · Page 5Linked to original sources
arXiv2000

CP and T violation in long baseline experiments with low energy neutrino

Stimulated by the idea of PRISM, a very high intensity muon ring with rather low energy, we consider possibilities of observing CP-violation effects in neutrino oscillation experiments. Destructive sum of matter effect and CP-violation effect can be avoided with use of initial $ν_{\rm e}$ beam. We finally show that the experiment with (a few) $\times$ 100 MeV of neutrino energy and (a few) $\times$ 100 km of baseline length, which is considered in this paper, is particularly suitable for a search of CP violation in view of 3-generation nature of CP violation.

hep-ph↗
arXiv2000

CP and T violation in long baseline experiments with low energy neutrino from muon storage ring

Stimulated by the idea of PRISM, a very high intensity muon ring with rather low energy, we consider possibilities of observing CP-violation effects in neutrino oscillation experiments. More than 10% of CP-violation effect can be seen within the experimentally allowed region. Destructive sum of matter effect and CP-violation effect can be avoided with use of initial nu_e beam. We finally show that the experiment with (a few) x 100 MeV of neutrino energy and (a few) x 100 km of baseline length, which is considered in this paper, is particularly suitable for a search of CP violation in view of statistical error.

hep-ph↗
arXiv1999

T-violation search with very long baseline neutrino oscillation experiments

We consider possibilities of observing T-violation effects in neutrino oscillation experiments with very long baseline (~ 10000 km) using low energy neutrino (~ several hundreds MeV). We show that the matter effect effectively changes only the first-second generation mixing angle, respecting solar neutrino deficits and atmospheric neutrino anomalies. The effective mixing of the first-second generation in the Earth grows up to maximum by resonance. This effect enables one to search T violation in case the first-second mixing angle is small. We discuss its implications to the observations of T-violation effects in long baseline experiments.

hep-ph↗
arXiv1999

CP- and T-Violation Effects in Long Baseline Neutrino Oscillation Experiments

We examine how large CP- and T-violation effects are allowed in long baseline neutrino experiments with three generations of neutrinos, considering both the solar neutrino deficit and the atmospheric neutrino anomaly. We considerd two cases: When we attribute only the atmospheric neutrino anomaly to neutrino oscillation and assume the constant transition probability of electron neutrino to explain the solar neutrino deficit, we may have large CP-violation effect. When we attribute both the atmospheric neutrino anomaly and the solar neutrino deficit to neutrino oscillation, we can see sizable T-violation effects. In this case, however, we cannot ignore the matter effect and we will not see the pure CP-violation effect. We also show simple methods how to separate pure CP violating effect from the matter effect. We give compact formulae for neutrino oscillation probabilities assuming one of the three neutrino masses (presumably tau neutrino mass) to be much larger than the other masses and the effective mass due to matter effect. Two methods are shown: One is to observe envelopes of the curves of oscillation probabilities as functions of neutrino energy; a merit of this method is that only a single detector is enough to determine the presence of CP violation. The other is to compare experiments with at least two different baseline lengths; this has a merit that it needs only narrow energy range of oscillation data.

hep-ph↗
arXiv1999

CP Violation and Matter Effect in Long Baseline Neutrino Oscillation Experiments

We show simple methods how to separate pure CP violating effect from matter effect in long baseline neutrino oscillation experiments with three generations of neutrinos. We give compact formulae for neutrino oscillation probabilities assuming one of the three neutrino masses (presumably tau-neutrino mass) to be much larger than the other masses and the effective mass due to matter effect. Two methods are shown: One is to observe envelopes of the curves of oscillation probabilities as functions of neutrino energy; a merit of this method is that only a single detector is enough to determine the presence of CP violation. The other is to compare experiments with at least two different baseline lengths; this has a merit that it needs only narrow energy range of oscillation data.

hep-ph↗
arXiv1998

Effects of Matter Density Fluctuation in Long Baseline Neutrino Oscillation Experiments

The effects of matter density fluctuation in long baseline neutrino oscillation experiments are studied. Effects of short wavelength fluctuations are in general irrelevant. Effects of long wavelength fluctuations must be checked on a case-by-case basis. As an example we checked the fluctuation effects and showed its irrelevance in a case of K2K experiments.

hep-ph↗
arXiv1998

Non-perturbative approach to the effective potential of the $λϕ^{4} theory at finite temperature

We construct a non-perturbative method to investigate the phase structure of the scalar theory at finite temperature. The derivative of the effective potential with respect to the mass square is expressed in terms of the full propagator. Under a certain approximation this expression reduces to the partial differential equation for the effective potential. We numerically solve the partial differential equation and obtain the effective potential non-perturbatively. It is found that the phase transition is of the second order. The critical exponents calculated in this method are consistent with the results obtained in Landau approximation.

hep-th↗
arXiv1997

Infra-Red Fixed Points in an Asymptotically Non-Free Theory

We investigate the infrared fixed point structure in asymptotically free and asymptotically non-free theory. We find that the ratios of couplings converge strongly to their infrared fixed points in the asymptotically non-free theory.

hep-ph↗
arXiv1997

Non-perturbative Evaluation of the Effective Potential of $λϕ^4$ Theory at Finite Temperature under the Super-Daisy Approximation

We calculate the effective potential of the scalar theory at finite temperature under the super-daisy approximation, after expressing its derivative with respect to mass square in terms of the full propagator. This expression becomes the self-consistent equation for the derivative of the effective potential. We find the phase transition is first order with this approximation. We compare our result with others.

hep-th↗
arXiv1997

CP and T violation test in neutrino oscillation

I examine how large violation of CP and T is allowed in long base line neutrino experiments. When we attribute both the atmospheric neutrino anomaly and the solar neutrino deficit to neutrino oscillation we may have a sizable T violation effect proportional to the ratio of two mass differences; it is difficult to see CP violation since we can't ignore the matter effect. I give a simple expression for T violation in the presence of matter.

hep-ph↗
arXiv1997

Predictions of $m_b/m_τ$ and $m_t$ in an Asymptotically Non-Free Theory

We discuss an extention of the Minimal Supersymmetric Standard Model (MSSM) with the 4th and anti-4th generations which have $SU(2)_L\times U(1)_Y$ invariant masses. Due to the the extra generations, all three running gauge couplings become asymptotically non--free while preserving gauge coupling unification at the GUT scale. We show that due to the asymptotically non--free character of the gauge couplings: (1) the top and bottom Yukawa couplings are strongly focused onto infrared fixed points as they are evolved down in scale making their values at $μ=\mz$ insensitive to their initial values at $μ=\mgut$; (2) the model predicts $\R(\mz) \equiv Y_b/Y_τ|_{μ=\mz}\approx 1.8$, which is consistent with the experimental value provided we take the ratio of Yukawa couplings at the GUT scale to be $\R(\mgut) = Y_b/Y_τ|_{μ= \mgut} = 1/3$; (3) the $t$ mass prediction comes out to be $\mt\approx 180\,\GeV$ which is also consistent with experiment.

hep-ph↗
arXiv1996

CP and T violation test in neutrino oscillation

We examine how large violation of CP and T is allowed in long base line neutrino experiments. When we attribute only the atmospheric neutrino anomaly to neutrino oscillation we may have large CP violation effect. When we attribute both the atmospheric neutrino anomaly and the solar neutrino deficit to neutrino oscillation we may have a sizable T violation effect proportional to the ratio of two mass differences; it is difficult to see CP violation since we can't ignore the matter effect. We give a simple expression for T violation in the presence of matter.

hep-ph↗
arXiv1996

Possible Candidates for SUSY E$_6$ GUT with an Intermediate Scale

We study the possibility of an intermediate scale existing in supersymmetric E$_6$ grand unified theories. The intermediate scale is demanded to be around $10^{12}$ GeV so that neutrinos can obtain masses suitable for explaining the experimental data on the deficit of solar neutrinos with the Mikheev-Smirnov-Wolfenstein solution and the existence of hot dark matter. We require that at the intermediate scale, a certain symmetry breakdown to the Standard Model symmetry. We show that only a few E$_6$ subgroups are likely to be realized as the intermediate symmetry, though there are many candidates for the intermediate symmetry in E$_6$ GUT.

hep-ph↗
arXiv1995

Duality of a Supersymmetric Standard Model without R parity

Recently one of the authors proposed a dual theory of a Supersymmetric Standard Model (SSM), in which it is naturally understood that at least one quark (the top quark) should be heavy, i.e., almost the same order as the weak scale, and the supersymmetric Higgs mass parameter $μ$ can naturally be expected to be small. Unfortunately, the model cannot possess Yukawa couplings of lepton sector. In this paper, we examine a dual theory of a Supersymmetric Standard Model without R parity. In this scenario, we can introduce Yukawa couplings of lepton sector. In order to induce the enough large Yukawa couplings of leptons, we must introduce fairly large R parity breaking terms, which may be observed in the near future.

hep-ph↗
arXiv1995

A SUSY SO(10) GUT with an Intermediate Scale

We examine a superpotential for an SO(10) GUT and show that if the parameters of the superpotential are in a certain region, the SO(10) GUT has an intermediate symmetry ${\rm SU(2)}_L \otimes {\rm SU(2)}_R \otimes {\rm SU(3)}_C \otimes {\rm U(1)}_{B-L}$ which breaks down to the group of the Standard Model at an intermediate scale $10^{10-12}$ GeV. In the model by the breakdown of the symmetry right-handed neutrinos acquire mass of the intermediate scale through a renormalizable Yukawa coupling.

hep-ph↗