Anisotropic Lattices and Dynamical Fermions

We report results from full QCD calculations with two flavors of dynamical staggered fermions on anisotropic lattices. The physical anisotropy as determined from spatial and temporal masses, their corresponding dispersion relations, and spatial and temporal Wilson loops is studied as a function of the bare gauge anisotropy and the bare velocity of light appearing in the Dirac operator. The anisotropy dependence of staggered fermion flavor symmetry breaking is also examined. These results will then be applied to the study of 2-flavor QCD thermodynamics.Comment: Lattice2001(spectrum

The D234 action for light quarks

We investigate a new light fermion action (the ``D234'' action), which is accurate up to \O(a^3) and tadpole-improved \O(a \alpha_s) errors. Using D234 with Symanzik- and tadpole-improved glue we find evidence that continuum results for the quenched hadron spectrum (pion, rho and nucleon) can be obtained on coarse lattices.Comment: Latex, 4 pages, submitted to Lattice '95 proceeding

Charmonia above the Deconfinement Phase Transition

Analyzing correlation functions of charmonia at finite temperature ($T$) on $32^3\times(32-96)$ anisotropic lattices by the maximum entropy method (MEM), we find that $J/\psi$ and $\eta_c$ survive as distinct resonances in the plasma even up to $T \simeq 1.6 T_c$ and that they eventually dissociate between $1.6 T_c$ and $1.9 T_c$ ($T_c$ is the critical temperature of deconfinement). This suggests that the deconfined plasma is non-perturbative enough to hold heavy-quark bound states. The importance of having sufficient number of temporal data points in the MEM analysis is also emphasized.Comment: Lattice2003(nonzero), 3 pages, 3 figure

Heavy quark action on the anisotropic lattice

We investigate the $O(a)$ improved quark action on anisotropic lattice as a potential framework for the heavy quark, which may enable precision computation of hadronic matrix elements of heavy-light mesons. The relativity relations of heavy-light mesons as well as of heavy quarkonium are examined on a quenched lattice with spatial lattice cutoff $a_\sigma^{-1} \simeq$ 1.6 GeV and the anisotropy $\xi=4$. We find that the bare anisotropy parameter tuned for the massless quark describes both the heavy-heavy and heavy-light mesons within 2% accuracy for the quark mass $a_\sigma m_Q < 0.8$, which covers the charm quark mass. This bare anisotropy parameter also successfully describes the heavy-light mesons in the quark mass region $a_\sigma m_Q \leq 1.2$ within the same accuracy. Beyond this region, the discretization effects seem to grow gradually. The anisotropic lattice is expected to extend by a factor $\xi$ the quark mass region in which the parameters in the action tuned for the massless limit are applicable for heavy-light systems with well controlled systematic errors.Comment: 11 pages, REVTeX4, 11 eps figure

Charmed hadron physics in quenched anisotropic lattice QCD

We investigate the anisotropic lattice with $O(a)$ improved quark action as a candidate of framework in which we can treat both the heavy and light quark region in the same manner and systematically reduce the systematic uncertainties. To examine applicability of anisotropic lattice, we calculate the charmed meson spectrum and decay constants in quenched approximation. We find consistent result with most advanced results on isotropic lattices.Comment: 3 pages, 1 figure, contribution to Fifth KEK Topical Conference - Frontiers in Flavor Physics -, Tsukuba, Japan, November 20-22, 200

Heavy-light meson in anisotropic lattice QCD

We examine whether the $O(a)$ improved quark action on anisotropic lattices can be used as a framework for the heavy quark, which enables precision computation of matrix elements of heavy-light mesons. To this end, it is crucial to verify that a mass independent and nonperturbative tuning of the parameters is possible. As a first step, we observe the dispersion relation of heavy-light mesons on a quenched lattice using the action which is nonperturbatively tuned only for the leading terms. On a lattice with the spatial cutoff $a_\sigma^{-1} \simeq$ 1.6 GeV and the anisotropy $\xi=4$, the relativity relation holds within 2% accuracy in the quark mass region $a_\sigma m_Q \leq 1.2$ with the bare anisotropy parameter tuned for the massless quark. We also apply the action to a calculation of heavy-light decay constants in the charm quark mass region.Comment: Lattice2002(heavyquark), 3 pages, 2 figure

Improved Gauge Actions on Anisotropic Lattices I

On anisotropic lattices with the anisotropy $\xi=a_\sigma/a_\tau$ the following basic parameters are calculated by perturbative method: (1) the renormalization of the gauge coupling in spatial and temporal directions, $g_\sigma$ and $g_\tau$, (2) the $\Lambda$ parameter, (3) the ratio of the renormalized and bare anisotropy $\eta=\xi/\xi_B$ and (4) the derivatives of the coupling constants with respect to $\xi$, $\partial g_\sigma^{-2}/\partial \xi$ and $\partial g_\tau^{-2}/\partial \xi$. We employ the improved gauge actions which consist of plaquette and six-link rectangular loops, $c_0 P(1 \times 1)_{\mu \nu} + c_1 P(1 \times 2)_{\mu \nu}$. This class of actions covers Symanzik, Iwasaki and DBW2 actions. The ratio $\eta$ shows an impressive behavior as a function of $c_{1}$, i.e.,$\eta>1$ for the standard Wilson and Symanzik actions, while $\eta<1$ for Iwasaki and DBW2 actions. This is confirmed non-perturbatively by numerical simulations in weak coupling regions. The derivatives $\partial g^{-2}_{\tau}/\partial \xi$ and $\partial g^{-2}_{\sigma}/\partial \xi$ also changes sign as $-c_{1}$ increases. For Iwasaki and DBW2 actions they become opposite sign to those for standard and Symanzik actions. However, their sum is independent of the type of actions due to Karsch's sum rule