arXiv subjects

Sinya Aoki

Publications and source records attributed to Sinya Aoki.

At least 199 records · Page 11Linked to original sources

arXiv2004

Perturbative Determination of Mass Dependent $O(a)$ Improvement Coefficients for the Vector and Axial Vector Currents with a Relativistic Heavy Quark Action

We carry out a perturbative determination of mass dependent renormalization factors and $O(a)$ improvement coefficients for the vector and axial vector currents with a relativistic heavy quark action, which we have designed to control $m_Qa$ errors by extending the on-shell $O(a)$ improvement program to the case of $m_Q \gg Λ_{\rm QCD}$ with $m_Q$ the heavy quark mass. We discuss what kind of improvement operators are required for the heavy-heavy and the heavy-light cases under the condition that the Euclidean rotational symmetry is not retained anymore because of the $m_Qa$ corrections. Our calculation is performed employing the ordinary perturbation theory with the fictitious gluon mass as an infrared regulator. We show that all the improvement coefficients are determined free from infrared divergences. Results of the renormalization factors and the improvement coefficients are presented as a function of $m_Q a$ for various improved gauge actions as well as the plaquette action.

hep-lat↗

arXiv2003

One-loop calculation of mass dependent ${\cal O}(a)$ improvement coefficients for the relativistic heavy quarks on the lattice

We carry out the one-loop calculation of mass dependent ${\cal O}(a)$ improvement coefficients in the relativistic heavy quark action recently proposed, employing the ordinary perturbation theory with the fictitious gluon mass as an infrared regulator. We also determine renormalization factors and improvement coefficients for the axial-vector current at the one-loop level. It is shown that the improvement coefficients are infrared finite at the one-loop level if and only if the improvement coefficients in the action are properly tuned at the tree level.

hep-lat↗

arXiv2003

A Perturbative Determination of Mass Dependent $O(a)$ Improvement Coefficients in a Relativistic Heavy Quark Action

We present the results for a perturbative determination of mass dependent improvement coefficients $ν$, $r_s$, $c_E$ and $c_B$ in a relativistic heavy quark action, which we have designed to control $m_Qa$ errors by extending the on-shell $O(a)$ improvement program to the case of $m_Q \gg Λ_{\rm QCD}$, where $m_Q$ is the heavy quark mass. The parameters $ν$ and $r_s$ are determined from the quark propagator and $c_E$ and $c_B$ are from the on-shell quark-quark scattering amplitude. We show that all the parameters, together with the quark wave function and the mass renormalization factors, are determined free from infrared divergences once their tree level values are properly tuned. Results of these parameters are shown as a function of $m_Q a$ for various improved gauge actions.

hep-lat↗

arXiv2003

A perturbative determination of O($a$) boundary improvement coefficients for the Schrödinger Functional coupling at 1-loop with improved gauge actions

We perturbatively determine O($a$) boundary improvement coefficients at 1-loop for the Schrödinger Functional coupling with improved gauge actions. These coefficients are required to implement the 1-loop O($a$) improvement in full QCD simulations for the coupling with the improved gauge actions. To this order, lattice artifacts of the step scaling function (SSF) for each improved gauge action are also investigated. Furthermore, we investigate the effect of the 1-loop O($a$) improvement to the SSF in numerical simulations of the pure SU(3) gauge theory.

hep-lat↗

arXiv2003

Chiral perturbation theory with Wilson-type fermions including $a^2$ effects: $N_f=2$ degenerate case

We have derived the quark mass dependence of $m_π^2$, $m_{\rm AWI}$ and $f_π$, using the chiral perturbation theory which includes the $a^2$ effect associated with the explicit chiral symmetry breaking of the Wilson-type fermions, in the case of the $N_f=2$ degenerate quarks. Distinct features of the results are (1) the additive renormalization for the mass parameter $m_q$ in the Lagrangian, (2) $O(a)$ corrections to the chiral log ($m_q\log m_q$) term, (3) the existence of more singular term, $\log m_q$, generated by $a^2$ contributions, and (4) the existence of both $m_q\log m_q$ and $\log m_q$ terms in the quark mass from the axial Ward-Takahashi identity, $m_{\rm AWI}$. By fitting the mass dependence of $m_π^2$ and $m_{\rm AWI}$, obtained by the CP-PACS collaboration for $N_f=2$ full QCD simulations, we have found that the data are consistently described by the derived formulae. Resumming the most singular terms $\log m_q$, we have also derived the modified formulae, which show a better control over the next-to-leading order correction.

hep-lat↗

arXiv2003

The Lattice $Λ$ Parameter in Domain Wall QCD

We evaluate the ratio of the scale parameter $Λ$ in domain wall QCD to the one in the continuum theory at one loop level incorporating the effect of massless quarks. We show that the Pauli-Villars regulator is required to subtract the unphysical massive fermion modes which emerge in the fermion loop contributions to the gluon self energy. Detailed results are presented as a function of the domain wall height $M$.

hep-lat↗

arXiv2003

Determination of the Improvement Coefficient c_SW up to One-Loop Order with the Conventional Perturbation Theory

We calculate the $O(a)$ improvement coefficient c_SW in the Sheikholeslami-Wohlert quark action for various improved gauge actions with six-link loops. We employ the conventional perturbation theory introducing the fictitious gluon mass to regularize the infrared divergence. Our results for some improved gauge actions are in agreement with those previously obtained with the Schr{ö}dinger functional method.

hep-lat↗

arXiv2003

A perturbative determination of O(a) boundary improvement coefficients for the Schrödinger Functional coupling at 1-loop with improved gauge actions

We determine O($a$) boundary improvement coefficients up to 1-loop level for the Schrödinger Functional coupling with improved gauge actions including plaquette and rectangle loops. These coefficients are required to implement 1-loop O($a$) improvement in full QCD simulations for the coupling with the improved gauge actions. To this order, lattice artifacts of step scaling function for each improved gauge action are also investigated. In addition, passing through the SF scheme, we estimate the ratio of $Λ$-parameters between the improved gauge actions and the plaquette action more accurately.

hep-lat↗

arXiv2002

Perturbative renormalization factors in domain-wall QCD with improved gauge actions

We evaluate renormalization factors of the domain-wall fermion system with various improved gauge actions at one loop level. The renormalization factors are calculated for quark wave function, quark mass, bilinear quark operators, three- and four-quark operators in modified minimal subtraction (MS-bar) scheme with the dimensional reduction(DRED) as well as the naive dimensional regularization(NDR). We also present detailed results in the mean field improved perturbation theory.

hep-lat↗

arXiv2001

Domain-wall fermions and chiral symmetries

We investigate chiral properties of the domain-wall fermion (DWF) system. After a brief introduction for the DWF, we summarize the recent numerical results on the chiral properties of the domain-wall QCD (DWQCD), which seem mutually inconsistent. We next derive a formula which connects a chiral symmetry breaking term in the five dimensional DWF Ward-Takahashi identity with the four-dimensional hermitian Wilson-Dirac operator. Based on this formula, we propose a solution, which resolves the inconsistency among recent numerical data, and give a consistent picture of the chiral properties of the DWQCD.

hep-lat↗

arXiv2001

Relativistic heavy quarks on the lattice

We investigate feasibility of relativistic approaches to the heavy quark physics on both anisotropic and isotropic lattices. Our peturbative calculation reveals that the anisotropic lattice is not theoretically adovantageous over the isotropic one to control $m_Q a$ errors. We instead propose a new relativistic approach to handle heavy quarks on the isotropic lattice.

hep-lat↗

arXiv2001

Relativistic Heavy Quarks on the Lattice

Lattice QCD should allow quantitative predictions for the heavy quark physics from first principles. Up to now, however, most approaches have based on the nonrelativistic effective theory, with which the continuum limit can not be taken in principle. In this paper we investigate feasibility of relativistic approaches to the heavy quark physics in lattice QCD. We first examine validity of the idea that the use of the anisotropic lattice could be advantageous to control the $m_Q a$ corrections. Our perturbative calculation, however, reveals that this is not true. We instead propose a new relativistic approach to handle heavy quarks on the isotropic lattice. We explain how power corrections of $m_Q a$ can be avoided and remaining uncertainties are reduced to be of order $(aΛ_{QCD})^2$.

hep-lat↗

arXiv2000

Unquenched QCD simulation results

The recent progress on unquenched QCD simulations is critically reviewed. After some discussions on problems and subtleties in unquenched simulations, hadron spectra obtained from both quenched and unquenched simulations are compared among various gauge and quark actions. It is found that the Edinburgh plot does not agree in the continuum limit between Wilson and KS quark actions even in quenched QCD. Dynamical quark effects on hadron spectra, in particular, on meson masses are then presented for Wilson-type quark actions. Finally dynamical quark effects on other quantities such as the topological susceptibility and the flavor-singlet meson mass are discussed.

hep-lat↗

arXiv2000

Perturbative renormalization factors of $ΔS = 1$ four-quark operators for domain-wall QCD

Renormalization factors for $ΔS =1$ four-quark operators in the effective weak Hamiltonian are perturbatively evaluated in domain-wall QCD. The one-loop corrections of $ΔS=1$ four-quark operators consist of two types of diagrams: one is gluon exchange between quark lines and the other is penguin diagrams containing quark loops. Combining both contributions, our results allow a lattice calculation of the amplitude for $K\to ππ$ decays with $O(g^2)$ corrections included.

hep-lat↗

arXiv2000

Domain Wall Fermions in Quenched Lattice QCD

We study the chiral properties and the validity of perturbation theory for domain wall fermions in quenched lattice QCD at beta=6.0. The explicit chiral symmetry breaking term in the axial Ward-Takahashi identity is found to be very small already at Ns=10, where Ns is the size of the fifth dimension, and its behavior seems consistent with an exponential decay in Ns within the limited range of Ns we explore. From the fact that the critical quark mass, at which the pion mass vanishes as in the case of the ordinary Wilson-type fermion, exists at finite Ns, we point out that this may be a signal of the parity broken phase and investigate the possible existence of such a phase in this model at finite Ns. The rho and pi meson decay constants obtained from the four-dimensional local currents with the one-loop renormalization factor show a good agreement with those obtained from the conserved currents.

hep-lat↗

arXiv1999

Lattice Calculations and Hadron Physics

We review progress in lattice QCD, focusing on efforts to calculate weak matrix elements relevant for the determination of the Cabibbo-Kobayashi-Maskawa matrix. Topics we discuss include light hadron spectrum and quark masses, CP-violation in K meson decays and weak matrix elements of heavy-light mesons.

hep-ph↗

arXiv1999

Perturbative renormalization factors of quark operators for domain-wall QCD

We calculate one-loop renormalization factors of several quark operators including bilinear, three- and four-quark operator for domain-wall fermion action. Since Green functions are constructed for external physical quark fields, our renormalization method is simple and can be easily applied to calculation of any quark operators. Our results show that these renormalized quark operators preserve several chiral properties of continuum massless QCD, which can be understood by the property of external quark line propagator.

hep-lat↗

arXiv1999

Perturbative renormalization factors of three- and four-quark operators for domain-wall QCD

Renormalization factors for three- and four-quark operators, which appear in the low energy effective Lagrangian of the proton decay and the weak interactions, are perturbatively calculated in domain-wall QCD. We find that the operators are multiplicatively renormalizable up to one-loop level without mixing with any other operators that have different chiral structures. As an application, we evaluate a renormalization factor for $B_K$ at the parameters where previous simulations have been performed, and find one-loop corrections to $B_K$ are 1-5% in these cases.

hep-lat↗