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Register a new userNonperturbative $O(a)$ improvement of the Wilson quark action with the RG-improved gauge action using the Schrodinger functional method
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We perform a nonperturbative determination of the $O(a)$-improvement coefficient $c_{rm SW}$ and the critical hopping parameter $kappa_c$ for $N_f$=3, 2, 0 flavor QCD with the RG-improved gauge action using the Schrodinger functional method. In order to interpolate $c_{rm SW}$ and $kappa_c$ as a function of the bare coupling, a wide range of $beta$ from the weak coupling region to the moderately strong coupling points used in large-scale simulations is studied. Corrections at finite lattice size of $O(a/L)$ turned out to be large for the RG-improved gauge action, and hence we make the determination at a size fixed in physical units using a modified improvement condition. This enables us to avoid $O(a)$ scaling violations which would remain in physical observables if $c_{rm SW}$ determined for a fixed lattice size $L/a$ is used in numerical simulations.
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We perform a non-perturbative determination of the O(a)-improvement coefficient c_SW for the Wilson quark action in three-flavor QCD with the plaquette gauge action. Numerical simulations are carried out in a range of beta=12.0-5.2 on a single lattice size of 8^3x16 employing the Schrodinger functional setup of lattice QCD. As our main result, we obtain an interpolation formula for c_SW and the critical hopping parameter K_c as a function of the bare coupling. This enables us to remove O(a) scaling violation from physical observables in future numerical simulation in the wide range of beta. Our analysis with a perturbatively modified improvement condition for c_SW suggests that finite volume effects in c_SW are not large on the 8^3x16 lattice. We investigate N_f dependence of c_SW by additional simulations for N_f=4, 2 and 0 at beta=9.6. As a preparatory step for this study, we also determine c_SW in two-flavor QCD at beta=5.2. At this beta, several groups carried out large-scale calculations of the hadron spectrum, while no systematic determination of c_SW has been performed.
We present the quark mass and axial current renormalization factors for the RG-improved Iwasaki gauge action and three flavors of the stout smeared $O(a)$-improved Wilson quark action. We employ $alpha=0.1$ and $n_{mathrm{step}}=6$ for the stout link smearing parameters and all links in the quark action are replaced with the smeared links. Using the Schr{o}dinger functional scheme we evaluate the renormalization factors at $beta=1.82$ where large scale simulations are being carried out.
We review a relativistic approach to the heavy quark physics in lattice QCD by applying a relativistic $O(a)$ improvement to the massive Wilson quark action on the lattice. After explaining how power corrections of $m_Q a$ can be avoided and remaining uncertainties are reduced to be of order $(aLambda_{rm QCD})^2$, we demonstrate a determination of four improvement coefficients in the action up to one-loop level in a mass dependent way. We also show a perturbative determination of mass dependent renormalization factors and $O(a)$ improvement coefficients for the vector and axial vector currents. Some preliminary results of numerical simulations are also presented.
We explore sea quark effects in the light hadron mass spectrum in a simulation of two-flavor QCD using the nonperturbatively O(a)-improved Wilson fermion action. In order to identify finite-size effects, light meson masses are measured on 12^3x48, 16^3x48 and 20^3x48 lattices with a~0.1 fm. On the largest lattice, where the finite-size effect is negligible, we find a significant increase of the strange vector meson mass compared to the quenched approximation. We also investigate the quark mass dependence of pseudoscalar meson masses and decay constants and test the consistency with (partially quenched) chiral perturbation theory.
We report on a calculation of the light hadron spectrum and quark masses in three-flavor dynamical QCD using the non-perturbatively O(a)-improved Wilson quark action and a renormalization-group improved gauge action. Simulations are carried out on a 16^3 times 32 lattice at beta=1.9, where a^{-1} simeq 2GeV, with 6 ud quark masses corresponding to m_{pi}/m_{rho} simeq 0.64-0.77 and 2 s quark masses close to the physical value. We observe that the inclusion of dynamical strange quark brings the lattice QCD meson spectrum to good agreement with experiment. Dynamical strange quarks also lead to a reduction of the uds quark masses by about 15%.
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