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Tadashi Yoshikawa

Publications and source records attributed to Tadashi Yoshikawa.

17 recordsLinked to original sources
arXiv2013

The Legacy of Hideki Yukawa, Sin-itiro Tomonaga, and Shoichi Sakata: Some Aspects from their Archives

Hideki Yukawa, Sin-itiro Tomonaga and Shoichi Sakata pioneered nuclear and particle physics and left enduring legacies. Their friendly collaboration and severe competition laid the foundation to bring up the active postwar generation of nuclear and particle physicists in Japan. In this presentation we illustrate milestones of nuclear and particle physics in Japan from 1930's to mid-1940's which have been clarified in Yukawa Hall Archival Library, Tomonaga Memorial Room and Sakata Memorial Archival Library.

physics.hist-ph↗
arXiv2008

Effect of Leptonic CP Phase in nu_mu --> nu_mu Oscillations

In the case of large 1-3 mixing angle as sin^2(2theta13 > 0.03, we investigate the possibility for measuring the leptonic CP phase by using only nu_mu --> nu_mu oscillations independently of nu_mu --> nu_e oscillations. As the result, we find that the CP phase can be measured best around the energy E=0.43 GeV and the baseline length L=5000km without strongly depending on the uncertainties of other parameters. In this region, the CP phase effect remains even after averaging over neutrino energy. We also find that there is the CP sensitivity even in the short baseline length L < 1000 km if Delta m_{31}^2 is determined with the uncertainty of about 0.1 . In the T2KK experiment, we explore the possibility for determining Delta m_{31}^2 by using one baseline from Tokai to Korea and then measuring the CP phase by using the baseline to Kamioka. As the result, we find that some information of the CP phase can be obtained from both measurements.

hep-ph↗
arXiv2007

Systematic Analysis of B --> K pi l^+ l^- Decay through Angular Decomposition

We investigate systematically how to extract new physics contributions in B --> K pi l^+ l^- decay by using the angular decomposition. The decomposition will enable us to define not only several CP averaged forward-backward (FB) asymmetries but also the direct CP asymmetry and the time-dependent mixing induced CP asymmetry for each FB asymmetry newly defined in the general 4 body angular space. The decay process involves several intermediate vector and scalar resonances as sources of strong phase difference through interference, therefore, one can expect largely enhanced CP asymmetries, if there exists any new physics with weak CP phases. The combined analysis of the FB and CP asymmetries will give us fruitful information about new physics contributions in detail.

hep-ph↗
arXiv2006

Measuring the Leptonic CP Phase in $ν_μ \to ν_μ$ Oscillations

In $ν_μ \to ν_μ$ oscillations, we find that the effect of the CP phase $δ$ becomes large in the region $E<2$ GeV and $L>2000$ km. In this region, the change of the probability in this channel reaches about 0.4 due to the CP phase effect beyond our expectation in the case of large 1-3 mixing angle. Furthermore, the CP phase effect have almost same sign over the region $E>0.5$ GeV so that one may find the signal of CP violation by measuring the total rate only. As an example, we use an experimental setup and demonstrate that the allowed region is limited to one by combined analysis of $ν_e$ and $ν_μ$ events although there remain three allowed regions by the analysis of $ν_e$ events alone.

hep-ph↗
arXiv2006

New Index of CP Phase Effect and $θ_{13}$ Screening in Long Baseline Neutrino Experiments

We introduce a new index of the leptonic CP phase dependence $I_{\rm CP}$ and derive the maximal condition for this index in a simple and general form. $I_{\rm CP}\simeq 100%$ may be realized even in the JPARC experiment. In the case that the 1-3 mixing angle can be observed in the next generation reactor experiments, namely $\sin^2 2θ_{13}>0.01$, and nevertheless $ν_e$ appearance signal cannot be observed in the JPARC experiment, we conclude that the CP phase $δ$ becomes a value around $135^{\circ}$ $(45^{\circ})$ for $Δm^2_{31}>0$ $(Δm^2_{31}<0)$ without depending the uncertainties of solar and atmospheric parameters.

hep-ph↗
arXiv2005

Possibility of Large EW Penguin contribution

We discuss a possibility of large electroweak(EW) penguin contribution in B-->K pi and pi pi. The recent experimental data may be still suggesting that there are some discrepancies between the data and theoretical estimations. In B --> K pi decays, to explain several theoretical relations among the branching ratios, a slightly large electroweak penguin contribution and large strong phase differences or quite large color suppressed tree contribution seem to be needed. The contributions should appear also in B --> pi pi. We show, as an example, a solution to solve the discrepancies in both B --> K pi and B --> pi pi. It may be suggesting to need the large electroweak penguin contribution with new weak phases and some SU(3) breaking effects by new physics in both QCD and electroweak penguin type processes.

hep-ph↗
arXiv2004

Large electroweak penguin contribution in B -> K pi and pi pi decay modes

We discuss about a possibility of large electroweak penguin contribution in B -> K pi and pi pi from recent experimental data. The experimental data may be suggesting that there are some discrepancies between the data and theoretical estimation in the branching ratios of them. In B -> K pi decays, to explain it, a large electroweak penguin contribution and large strong phase differences seem to be needed. The contributions should appear also in B -> pi pi. We show, as an example, a solution to solve the discrepancies in both B -> K pi and B -> pi pi. However the magnitude of the parameters and the strong phase estimated from experimental data are quite large compared with the theoretical estimations. It may be suggesting some new physics effects are including in these processes. We will have to discuss about the dependence of the new physics. To explain both modes at once, we may need large electroweak penguin contribution with new weak phases and some SU(3) breaking effects by new physics in both QCD and electroweak penguin type processes.

hep-ph↗
arXiv2003

Large electroweak penguin contribution in B --> K pi modes

I discuss about a possibility of large electroweak penguin contribution in B --> K pi. To satisfy several relations among the branching ratios, we need large electroweak penguin contribution. The magnitude is larger than the theoretical estimation in the SM so that it may be including some new physics effects.

hep-ph↗
arXiv2003

A Possibility of large electro-weak penguin contribution in B -> K pi modes

We discuss about a possibility of large electro-weak penguin contribution in B -> K pi from recent experimental data. The several relations among the branching ratios which realize when the contributions from tree type and electro-weak penguin are small compared with the gluon penguin and can be treated as the expansion parameters do not satisfy the data. The difference comes from the r^2 terms which is the square of the ratio with the gluon penguin and the main contribution comes from electro-weak penguin. We find that the contribution from electro-weak penguin may be large to explain the experimental data. If the magnitude estimated from experiment is quite large compared with the theoretical estimation, then it may be including some new physics effects.

hep-ph↗
arXiv2003

What can we learn from phi_1 and B_d^0 -> pi^+ pi^- ?

We discuss what we can understand from $ϕ_1$ and $B^0_d\to π^+ π^- $ decay mode. Using a convention without weak phases $ϕ_2$ and $ϕ_3$, we can solve the parameters from the time-depended CP asymmetry. If we can put a condition the contribution from penguin except for the CKM factor including in the diagram is small, then we can lead the allowed region of $R_t$ or $ϕ_2$ by using the convention.

hep-ph↗
arXiv2002

Majorana Mass Zeroes from Triplet VEV without Majoron Problem

It is shown how to obtain recently-proposed two-zero Majorana mass textures in models with three Higgs triplets with small VEVs and a sufficiently massive triplet Majoron by using abelian discrete symmetries. It is briefly discussed how in SU(5) grand unification where the triplets occur in {\bf 15}'s the neutrino textures can be related to up- and down- quark mass textures.

hep-ph↗
arXiv2001

Zee Model Confronts SNO Data

We reexamine the solution of the minimal Zee model by comparing with the data of the SNO experiment, and conclude that the model is strongly disfavored but not yet excluded by the observations. Two extensions of the Zee model are briefly discussed both of which introduce additional freedom and can accommodate the data.

hep-ph↗
arXiv2001

The Width Difference of $B_d$ Mesons

We estimate $\dg/Γ_d$, including $1/m_b$ contributions and part of the next-to-leading order QCD corrections. We find that adding the latter corrections decreases the value of $\dg/Γ_d$ computed at the leading order by a factor of almost 2. We also show that under certain conditions an upper bound on the value of $\dg/Γ_d$ in the presence of new physics can be derived. With the high statistics and accurate time resolution of the upcoming LHC experiment, the measurement of $\dg$ seems to be possible. This measurement would be important for an accurate measurement of $\sin(2β)$ at the LHC. In addition, we point out the possibility that the measurement of the width difference leads to a clear signal for new physics.

hep-ph↗
arXiv2001

Model of Soft CP Violation

We propose a model of soft CP violation that evades the strong CP problem and can describe observed CP violation in the neutral kaon sector, both direct and indirect. Our model requires two ``duark'' mesons carrying quark number two that have complex (CP-violating) bare masses and are coupled to quark pairs. Aside from the existence of these potentially observable new particles with masses of several hundred GeV, we predict a flat unitarity triangle ({\it i.e.,} no observable direct CP violation in the $B$-meson sector) and a possibly anomalous branching ratio for the decay mode $K^+\to π^++\barν ν$.

hep-ph↗
arXiv1995

The Effects of a Vector-like Doublet as the Fourth Generation to $R_b$

We study the effects of a vector-like SU(2) doublet quarks as the fourth generation on $R_b$ and $R_c$. By considering the constraint from the experimental data of forward-backward asymmetry, $A_{FB}^b$ and $A_{FB}^c$,as well as FCNC among light quarks, we show that there is an allowed region of parameters for $R_b$ but not for $R_c$.

hep-ph↗
arXiv1995

The Oblique Corrections from the Diagonal ETC Interaction

We study the effect of the diagonal extended technicolor(ETC) gauge boson on the oblique correction parameters. It is shown that in the $T$ parameter is unacceptably large when the $Zbb$ vertex correction and $S$ parameter are consistent with the experiments in the ETC model.

hep-ph↗