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We present our study on B → pi;lν semileptonic decay form factors using NRQCD action for heavy quark. In the analysis, we use the form factors f1(·kπ) and f2(·kπ) defined in the context of heavy quark effective theory by Burdman et al.. Since the NRQCD action for heavy quark respects the heavy quark symmetry, our results are described by the HQET form factors most naturally. From a quenched lattice QCD simulation at β=5.9 on a 163 × 48 lattice, we obtain the form factors f1(·kπ) and f2(·kπ), and find that their 1/mB correction is small. The limit of physical heavy and light quark masses can be reached without introducing any model function, and we obtain a prediction for the differential decay rate dΓ/dq2. We also discuss the soft pion limit of the form factors.

CP-PACS and JLQCD Collaborations are carrying out a joint project of the 2+1 flavor full QCD with the RG-improved gauge action and the non-perturbatively ${\cal O}(a)$-improved Wilson quark action. This simulation removes quenching effects of all three light quarks, which is the last major uncertainty in lattice QCD. In this report we present our results for the light meson spectrum and quark masses on a $20^3\times 40$ lattice at the lattice spacing $a\simeq 0.10$ fm., 3 pages, 3 figures, Talk presented at Lattice2004(spectrum), Fermilab, June 21-26, 2004

We present the final results of the JLQCD calculation of the light hadron spectrum and quark masses with two flavors of dynamical quarks using the plaquette gauge action and fullyO(a)-improved Wilson quark action at β = 5.2. We observe that sea quark effects lead to a closer agreement of the strange meson and baryon masses with experiment and a reduction of quark masses by 20–30%.0

We present a two-flavor dynamical QCD calculation of the B meson B parameters and decay constant. We use NRQCD for heavy quark and the nonperturbatively O(a)-improved Wilson action for light quark at $\beta$=5.2 on a $20^3\times 48$ lattice. We confirm that the sea quark effect increases the heavy-light decay constant, while estimate of its magnitude depends significantly on the fitting form in the chiral extrapolation. For the B parameters, on the other hand, we do not find a significant sea quark effect. The chiral extrapolation with logarithmic term is examined for both quantities and compared with the prediction of ChPT., Comment: 3 pages, 3 figures, Lattice2001(heavyquark)

Using the lattice NRQCD action for heavy quark, we calculate the heavy quark expansion parameters $\mu_{\pi}^2$ and $\mu_G^2$ for heavy-light mesons and heavy-light-light baryons. The results are compared with the mass differences among heavy hadrons to test the validity of HQET relations on the lattice., Comment: Lattice2001(heavyquark), 3 pages, 4 figures

JLQCD collaboration recently started the N f = 3 QCD simulations with the O ( a )-improved Wilson fermion action employing an exact fermion algorithm developed for odd number of quark flavors. It is found that this theory has an unexpected non-trivial phase structure in the (β, κ) plane even at zero temperature. A detailed study is made to understand the nature of the observed phase transitions and to find the way of avoiding untolerably large lattice artifacts associated with the phase transition.

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., 3 pages, 3 figures, Lattice2001(spectrum)

We present results for I=2 pion scattering length with the Wilson fermions in the quenched approximation. The finite size method presented by L\"uscher is employed, and calculations are carried out at $\beta=5.9$, 6.1, and 6.3. In the continuum limit, we obtain a result in reasonable agreement with the experimental value., Comment: LATTICE99(matrixelement), 3 pages, 4 eps figures

We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass $M_{PS}$. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the $O(a)$-improved clover action at $\beta=5.9$ on a $16^3\times 40$ and $24^3\times 64$ lattice. We find that a weak dependence of form factors on $M_{PS}$ observed in previous studies in the region of charm quark persists up to the region of$b$ quark. The soft pion relation $f^0(q^2_{max})=f_B/f_\pi$ is examined and found to be largely violated., Comment: 3 pages, latex source-file, 4 figures as epsf-file, uses espcrc2.sty. Talk presented by S. Tominaga at Lattice 97, Edinburgh, Scotland, 22-26 Jul 1997

We propose a non-perturbative method to determine the mixing coefficients of $\Delta s=2$ four-quark operators for the Wilson quark action using chiral Ward identities. The method is applied to calculate B_K in quenched QCD., Comment: 3 pages including 3 figures, Talk presented at LATTICE96(phenomenology) by Y. Kuramashi

We explore the problems in calculating the decay constant for heavy-light mesons using the quenched Wilson quark action for both heavy and light quarks. We find that the continuum limit of the decay constant is reasonably converged among different prescriptions after the continuum limit is taken. A number of technical problems associated with prescriptions are also addressed., Comment: 3 pages including 5 figures, Talk presented at LATTICE96(heavy quarks) by S. Hashimoto

We test the one-loop chiral perturbation theory formula on unquenched lattice data of pseudoscalar meson decay constants. The chiral extrapolation including the effect of the chiral logarithm is attempted and its uncertainty is discussed.

A new study is reported of a lattice QCD calculation of the $K^+\to\pi^+ \pi^0 $ decay amplitude with the Wilson quark action in the quenched approximation at $\beta=6.1$. The amplitude is extracted from the $K\to\pi\pi$ Green function, and a conversion to the continuum value is made employing a recent one-loop calculation of chiral perturbation theory. The result is consistent with the experimental value if extrapolated to the chiral limit., Comment: LaTeX, 3 pages, 3 figures, uses espcrc2 and epsfig. Talk presented at Lattice '97, Edinburgh, Scotland, July 1997