arXiv subjects

T. Kurimoto

Publications and source records attributed to T. Kurimoto.

16 recordsLinked to original sources

arXiv2010

Physics at Super B Factory

This report presents the results of studies that investigate the physics reach at a Super $B$ factory, an asymmetric-energy $e^+e^-$ collider with a design luminosity of $8 \times 10^{35}$ cm$^{-2}$s$^{-1}$, which is around 50 times as large as the peak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented.

hep-ex↗

arXiv2007

Gluonic contribution to $B\to η^{(\prime)}$ form factors

We calculate the flavor-singlet contribution to the $B\toη^{(\prime)}$ transition form factors from the gluonic content of the $η^{(\prime)}$ meson in the large-recoil region using the perturbative QCD approach. The formulation for the $η$-$η'$ mixing in the quark-flavor and singlet-octet schemes is compared, and employed to determine the chiral enhancement scales associated with the two-parton twist-3 $η^{(\prime)}$ meson distribution amplitudes. It is found that the gluonic contribution is negligible in the $B\toη$ form factors, and reaches few percents in the $B\toη'$ ones. Its impact on the accommodation of the measured $B\toη^{(\prime)} K$ branching ratios in the perturbative QCD and QCD-improved factorization approaches is elaborated.

hep-ph↗

arXiv2005

Nonfactorizable contributions to $B \to D^{(*)} M$ decays

While the factorization assumption works well for many two-body nonleptonic $B$ meson decay modes, the recent measurement of $\bar B\to D^{(*)0}M^0$ with $M=π$, $ρ$ and $ω$ shows large deviation from this assumption. We analyze the $B\to D^{(*)}M$ decays in the perturbative QCD approach based on $k_T$ factorization theorem, in which both factorizable and nonfactorizable contributions can be calculated in the same framework. Our predictions for the Bauer-Stech-Wirbel parameters, $|a_2/a_1|= 0.43\pm 0.04$ and $Arg(a_2/a_1)\sim -42^\circ$ and $|a_2/a_1|= 0.47\pm 0.05$ and $Arg(a_2/a_1)\sim -41^\circ$, are consistent with the observed $B\to Dπ$ and $B\to D^*π$ branching ratios, respectively. It is found that the large magnitude $|a_2|$ and the large relative phase between $a_2$ and $a_1$ come from color-suppressed nonfactorizable amplitudes. Our predictions for the ${\bar B}^0\to D^{(*)0}ρ^0$, $D^{(*)0}ω$ branching ratios can be confronted with future experimental data.

hep-ph↗

arXiv2004

Physics at Super B Factory

This report presents the results of studies that investigate the physics reach at a Super B factory, an asymmetric-energy e^+e^- collider with a design luminosity of 5 x 10^35 cm^-2s^-1, which is around 40 times as large as the peak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented. The sensitivity studies are a part of the activities associated with the preparation of a Letter of Intent for SuperKEKB, which has been submitted recently.

hep-ex↗

arXiv2002

$B \to D^{(*)}$ form factors in perturbative QCD

We calculate the $B\to D^{(*)}$ form factors in the heavy-quark and large-recoil limits in the perturbative QCD framework based on $k_T$ factorization theorem, assuming the hierachy $M_B\gg M_{D^{(*)}}\gg \barΛ$, with the $B$ meson mass $M_B$, the $D^{(*)}$ meson mass $M_{D^{(*)}}$, and the heavy meson and heavy quark mass difference $\barΛ$. The qualitative behavior of the light-cone $D^{(*)}$ meson wave function and the associated Sudakov resummation are derived. The leading-power contributions to the $B\to D^{(*)}$ form factors, characterized by the scale $\barΛ\sqrt{M_B/M_{D^{(*)}}}$, respect the heavy-quark symmetry. The next-to-leading-power corrections in $1/M_B$ and $1/M_{D^{(*)}}$, characterized by a scale larger than $\sqrt{\barΛM_B}$, are estimated to be less than 20%. The $D^{(*)}$ meson wave function is determined from the fit to the observed $B\to D^{(*)} lν$ decay spectrum, which can be employed to make predictions for nonleptonic decays, such as $B\to D^{(*)}π(ρ)$.

hep-ph↗

arXiv2002

$|V_{ub}|$ determination by $B \to D_s π$

We investigate $\ovar{B^0} \to D_s^- π^+$ decay in perturbative QCD approach which has recently been applied to $B$ meson decays. $\ovar{B^0} \to D_s^- π^+$ decay (and its charge conjugated mode) can be one of the hopeful modes to determine $|V_{ub}|$ since it occurs through $b \to u$ transition only. We estimate both factorizable and non-factorizable contribution, and show that the non-factorizable contribution is much less than the factorizable one. Our calculation gives ${BR}(\ovar{B^0} \to D_s^- π^+) = (50 \sim 70) \times f_{Ds}^2|{V_{ub}}{V_{cs}}|^2$.

hep-ph↗

arXiv2001

Updates of $W_R$ effects on CP angles determination in B decays

The recently observed CP violation in B decay and $B$-$\ovar{B}$ mixing data put constraints on the mass of $W_R$ and the parameters of the right-handed current quark mixing matrix $V^R$ in $SU(2)_L \times SU(2)_R\times U(1)$ gauge model. It is shown that the allowed region of parameters are severely restricted for light $W_R$ with mass on the order of 1 TeV. There exist sets of parameters which can accommodate large CP violation as measured by Belle, $\sin2ϕ_1|_{exp}\simeq 1$, for $M_{W_R}=1 \sim 10$ TeV.

hep-ph↗

arXiv2001

Leading-power contributions to $B\toπ,ρ$ transition form factors

We calculate the $B\toπ,ρ$ transition form factors in the framework of perturbative QCD to leading power of $1/M_B$, $M_B$ being the $B$ meson mass. We explain the basic principle by discussing the pion electromagnetic form factor. It is shown that the logarithmic and linear singularities occurring at small momentum fractions of light meson distribution amplitudes do not exist in a self-consistent perturbative analysis, which includes $k_\perp$ and threshold resummations.

hep-ph↗

arXiv1997

Toward the second stage at B factory

The measurement and precision at B physics experiment are reviewed by taking into account of the numbers of B mesons to be produced in the future experimental projects. With $10^9$ or more B mesons we will be able to fix the parameters in Kobayashi-Maskawa matrix elements or find a signal of new physics.

hep-ph↗

arXiv1997

New Physics and CP Angles Measurement at B Factory

We have analyzed how much the $CP$ angles to be measured at B factories can deviate from the geometrical ones defined in unitarity triangle under the existence of new physics. The measurements are given in rephasing invariant form. If KM matrix is not a $3\times 3$ and unitary matrix, $\tildeϕ_1$ and $\tildeϕ_3$ is affected, and the value of $\tildeϕ_3$ depends on the decay mode. The deviation is constrained to be less than the experimental precision attained in the next decade by the available data of the magnitude of KM matrix elements. Deviation of the sum of three angles from $π$ cannot be detected unless new physics contributes significantly to $b$ decay or $D$ meson system.

hep-ph↗

arXiv1997

A Note on CP Invariance and Rephasing Invariance

CP invariance condition and rephasing invariance in KM scheme of CP violation is discussed. The CP violation measures in B physics, corresponding to the three angles of unitarity triangle are given in rephasing invariant form. With the obtained results it is shown that the sum of the three CP angles to be measured at B factories becomes $π$ even if the Kobayashi-Maskwa matrix is not a $3\times 3$ unitary matrix under reasonable assumptions.

hep-ph↗

arXiv1995

$W_R$ effects on $CP$ angles determination at a $B$ factory

The right-handed charged current gauge boson $W_R$ can affect significantly on the determination of the $CP$ violation angles to be measured at $B$ factories if the right-handed current quark mixing matrix $V^R$ is taken to a specific form to satisfy the bounds by neutral $K$ meson systems. The $W_R$ contribution can be sizable in $B^0$-$\overline{B^0}$ mixing and tree level $b$ quark decay. The deviation of $CP$ angles in unitarity triangle from the standard model values can be as large as $-37^\circ$ or $ +22^\circ$ for $ϕ_3$ ($γ$), and $66^\circ \sim 115^\circ$ for $ϕ_1$ ($β$) and $ϕ_2$ ($α$).

hep-ph↗

arXiv1995

On the Phase of $B^0$--$\bar {B^0}$ Mixing Matrix Elements in the SUSY Standard Model

It is shown that the complex phase of $B^0$--$\bar {B^0}$ mixing matrix element is same as that of the standard model one up to the minor correction of the order of $(m_c/m_t)^2$ or less in the SUSY standard model. This conclusion is valid as far as the Yukawa coupling constants are perturbative and realistic, and can be available for other realistic models where generation mixing and CP violation are solely due to Yukawa interaction among quarks and Higgs doublets.

hep-ph↗

arXiv1993

Heavy meson effective thoery with 1/M_Q correction

We construct an effective Lagrangian of heavy and light mesons with $1/M_Q$ correction. The Lagrangian is constructed model independent way by using only the information of the symmetry of QCD. Reparameterisation invariance at the meson level is taken into account for the consistency of the theory. The partial decay width of the process $D^{*+} \rightarrow D^0 π^+$ and the form factors of the process ${\bar B}^0 \rightarrow π^+ l {\bar ν}$ are calculated with the $1/M_Q$ correction. We also introduce the light vector mesons based on the approach of the hidden local symmetry. The form factors of the process ${\bar B}^0 \rightarrow ρ^+ l {\bar ν}$ are calculated with thus introduced $ρ$-meson. These results are easily translated to the $D$-meson semileptonic decays.

hep-ph↗

arXiv1993

Chiral Lagrangian with higher resonances and flavour $ SU(3) $ breaking

A chiral Lagrangian with $ SU(3) $ breaking and higher resonances is proposed. In this model, the $ SU(3) $ breaking structure in vector-pseudoscalar sector is realized with the decay constants of pseudoscalar mesons and the masses of vector mesons used as inputs. We examine whether the resulting $ SU(3) $ breaking effect in the charge radii of pseudoscalar mesons is consistent with the experimental facts.

hep-ph↗

arXiv1993

Unified Description of Hadrons and Heavy Hadron Decays

We construct an effective Lagrangian which describes interactions of heavy and light hadrons utilizing the chiral flavor symmetry for light quarks and heavy quark symmetry. For both light and heavy sector we include pseudo scalars, vectors and baryons in the Lagrangian. Heavy hadron decays are discussed as application of our formalism. The $D_s$ decay constant and the coupling constant among heavy meson, heavy vector meson and light meson are fitted from the experimental data of $D^0 \rightarrow K^- e^+ν_e$ decay. We also point out the possibility of model independent determination of $|V_{ub}|$ from $Λ_b \rightarrow p l \bar ν$ decay.

hep-ph↗