Y. Kuramashi

Light hadron spectroscopy with two flavors of O(a)-improved dynamical quarks

We present a high statistics study of the light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks. Numerical simulations are carried out using the plaquette gauge action and the O(a)-improved Wilson quark action at \beta=5.2, where the lattice spacing is found to be a=0.0887(11)fm from \rho meson mass, on a 20^3\times 48 lattice. At each of five sea quark masses corresponding to m_{PS}/m_{V} \simeq 0.8-0.6, we generate 12000 trajectories using the symmetrically preconditioned Hybrid Monte Carlo algorithm. Finite spatial volume effects are investigated employing 12^3 \times 48, 16^3 \times 48 lattices. We also perform a set of simulations in quenched QCD with the same lattice actions at a similar lattice spacing to those for the full QCD runs. In the meson sector we find clear evidence of sea quark effects. The J parameter increases for lighter sea quark masses, and the full QCD meson masses are systematically closer to experiment than in quenched QCD. Careful finite-size studies are made to ascertain that these are not due to finite-size effects. Evidence of sea quark effects is less clear in the baryon sector due to larger finite-size effects. We also calculate light quark masses and find m_{ud}^{MS}(2GeV) =3.223(+0.046/-0.069)MeV and m_s^{MS}(2GeV)=84.5(+12.0/-1.7)MeV which are about 20% smaller than in quenched QCD.

B0−B¯0Mixing in Unquenched Lattice QCD

We present an unquenched lattice calculation for the B(0)-B(0) transition amplitude. The calculation, carried out at an inverse lattice spacing 1/a=2.22(4) GeV, incorporates two flavors of dynamical quarks described by the O(a)-improved Wilson fermion action and heavy quarks described by nonrelativistic QCD. Particular attention is paid to the uncertainty that arises from the chiral extrapolation, especially the effect of pion loops, for light quarks, which we find could be sizable for the leptonic decay constant, whereas it is small for the B parameters. We obtain f(B(d))=191(10)(+12-22) MeV, f(B(s))/f(B(d))=1.13(3)(+13-2), B(B(d))(m(b))=0.836(27)(+56-62), B(B(s))/B(B(d))=1.017(16)(+56-17), and xi=1.14(3)(+13-2), where the first error is statistical, and the second is systematic, including uncertainties due to chiral extrapolation, finite lattice spacing, heavy quark expansion, and perturbative operator matching.

Nonperturbative Determination of Quark Masses in Quenched Lattice QCD with the Kogut-Susskind Fermion Action

We report results of quark masses in quenched lattice QCD with the Kogut-Susskind fermion action, employing the Reguralization Independent scheme (RI) of Martinelli et al. to non-perturbatively evaluate the renormalization factor relating the bare quark mass on the lattice to that in the continuum. Calculations are carried out at \beta=6.0, 6.2, and 6.4, from which we find

Charmed baryons at the physical point in 2+1 flavor lattice QCD

m^{\bar{MS}}_{ud} (2 GeV)= 4.23(29) MeV

Hybrid Quarkonia on Asymmetric Lattices

for the average up and down quark mass and, with the

Exploratory Study of Nucleon-Nucleon Scattering Lengths in Lattice QCD

\phi

B meson decay constant from two-flavor lattice QCD with non-relativistic heavy quarks

meson mass as input,

Differential decay rate of B→πlν semileptonic decay with lattice nonrelativistic QCD

m^{\bar{MS}}_{s} (2 GeV)= 129(12) MeV

Kaon B parameter with the Wilson quark action using chiral Ward identities

for the strange mass in the continuum limit. These values are about 20% larger than those obtained with the one-loop perturbative renormalization factor.

B0−B0mixing in quenched lattice QCD

We investigate the charmed baryon mass spectrum using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 32 3 × 64 lattice. The dynamical updown and strange quark masses are tuned to their physical values, reweighted from those employed in the configuration generation. At the physical point, the inverse lattice spacing determined from the baryon mass gives a 1 = 2.194(10) GeV, and thus the spatial extent becomes L = 32a = 2.88(1) fm. Our results for the charmed baryon masses are consistent with experimental values, �