Thermodynamic properties of QCD with two flavors of Wilson-type lattice quarks

I report on a study of finite temperature QCD by the CP-PACS Collaboration toward a precise determination of the equation of state with dynamical u,d quarks. Based on a systematic simulation using improved Wilson-type quarks on lattices with temporal size $N_t=4$ and 6, the energy density and pressure are calculated as functions of temperature and renormalized light quark mass in the range $T/T_c \approx 0.7$--2.5 and $m_{\rm PS}/m_{\rm V} = 0.65$--0.95. Results for $N_t=4$ are found to contain significant scaling violations, while results for $N_t=6$ are suggested to be not far from the continuum limit. On the other hand, the quark mass dependence in the EOS turned out to be small for m_{\rm PS}/m_{\rm V} \simlt 0.8.Comment: Talk presented at Statistical QCD, Aug. 26-30, 2001, Bielefeld, Germany. LaTeX2e, 6 pages, 4 PS figures, espcrc1.sty neede

New results on cut-off effects in spectroscopy with the fixed point action

Our study on the cut-off effects in quenched light hadron spectroscopy and pion scattering length with the fixed point action is extended by results obtained at a lattice spacing a=0.102 fm in a box of size L=1.8 fm. The cut-off effects are small, but clearly seen as the resolution is increased from a=0.153 fm to a=0.102 fm. In the quark mass region where the errors are small and under control, our results on the APE plot lie close to the extrapolated numbers of the CP-PACS Collaboration.Comment: 15 pages, 11 figures, reference correcte

Strange quark mass from Finite Energy QCD sum rules to five loops

The strange quark mass is determined from a new QCD Finite Energy Sum Rule (FESR) optimized to reduce considerably the systematic uncertainties arising from the hadronic resonance sector. As a result, the main uncertainty in this determination is due to the value of $\Lambda_{QCD}$. The correlator of axial-vector divergences is used in perturbative QCD to five-loop order, including quark and gluon condensate contributions, in the framework of both Fixed Order (FOPT), and Contour Improved Perturbation Theory (CIPT). The latter exhibits very good convergence, leading to a remarkably stable result in the very wide range $s_0 = 1.0 - 4.0 {GeV}^2$, where $s_0$ is the radius of the integration contour in the complex energy (squared) plane. The value of the strange quark mass in this framework at a scale of 2 GeV is $m_s(2 {GeV}) = 95 \pm 5 (111 \pm 6) {MeV}$ for $\Lambda_{QCD} = 420 (330) {MeV}$, respectively.Comment: Additional comments added at the end of the Conclusions, and one extra reference is given. A note added in proof uses the most recent determination of Lambda_QCD from ALEPH to narrow down the predictio

Do we understand the unquenched value of fB?

I review our qualitative understanding of the increase in the value of the B meson decay constant (fB), when dynamical fermions are included in lattice QCD calculations.Comment: 4 pages. Talk at UK Phenomenology Workshop on Heavy Flavour and CP Violation, Durham, 17 - 22 September 2000 (Minor typo fixed

I=2 Pion Scattering Length and Phase Shift with Wilson Fermions

We present preliminary results of scattering length and phase shift for I=2 S-wave $\pi\pi$ system with the Wilson fermions in the quenched approximation. The finite size method presented by L\"uscher is employed, and calculations are carried out at $\beta=5.9$ on a $24^3\times 60$ and $32^3\times 60$ lattice.Comment: Lattice2001(spectrum

I=2 pion-pion scattering phase shift in the continuum limit calculated with two-flavor full QCD

We present a calculation of the scattering phase shift for the I=2 S-wave pion-pion system in the continuum limit with two-flavor full QCD. Calculations are made at three lattice spacings, using the finite volume method of L\"uscher in the center of mass frame, and its extension to the laboratory frame.Comment: Lattice2003(spectrum), 3 page

Dynamical fermions on anisotropic lattices

We report on our study of two-flavor full QCD on anisotropic lattices using $O(a)$-improved Wilson quarks coupled with an RG-improved glue. The bare gauge and quark anisotropies corresponding to the renormalized anisotropy $\xi=a_s/a_t = 2$ are determined as functions of $\beta$ and $\kappa$, using the Wilson loop and the meson dispersion relation at several lattice cutoffs and quark masses.Comment: Lattice2002(improve), 3 pages, 3 figure

Charmed meson spectra and decay constants with one-loop O(a)O(a) improved relativistic heavy quark action

We calculate charmed meson spectra and decay constants in lattice QCD employing one-loop $O(a)$ improved heavy quark action and axial-vector currents. In quenched simulations at $a \sim 0.1$ fm with the plaquette gauge action as well as a renormalization-group improved one, it is shown that the deviation from the continuum dispersion relation and the violation of space-time symmetry for the pseudoscalar meson decay constants are substantially reduced, once the $O(a)$ improvement is applied. Preliminary results with two flavors of dynamical quarks are also presented.Comment: 3 pages, 4 figure, talk presented at Lattice2004(heavy), Fermilab, June 21-26, 200