M. Fukugita

Quenched Light Hadron Spectrum

We present results of a large-scale simulation for the flavor nonsinglet light hadron spectrum in quenched lattice QCD with the Wilson quark action. Hadron masses are calculated at four values of lattice spacing in the range a approximately 0.1-0.05 fm on lattices with a physical extent of 3 fm at five quark masses corresponding to m(pi)/m(rho) approximately 0.75-0.4. The calculated spectrum in the continuum limit shows a systematic deviation from experiment, though the magnitude of deviation is contained within 11%. Results for decay constants and light quark masses are also reported.

Atmospheric neutrino oscillation and a phenomenological lepton mass matrix

We propose simple phenomenological lepton mass matrices which describe the three neutrinos almost degenerate in mass, leading to a very large mixing angle between

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

\nu_\mu

Phase structure and critical temperature of two-flavor QCD with a renormalization group improved gauge action and clover improved Wilson quark action

and

Equation of state for pure SU(3) gauge theory with renormalization group improved action

\nu_\tau

Light hadron spectrum and quark masses from quenched lattice QCD

, as consistent with a recent report on atmospheric neutrino oscillation from the Superkamiokande collaboration. Our matrix model also gives

B0−B¯0Mixing in Unquenched Lattice QCD

\nu_e-\nu_\mu

Nucleon decay matrix elements from lattice QCD

mixing in agreement with the value required for neutrino oscillation to explain the solar neutrino problem.

Kaon B parameter from quenched Lattice QCD

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.

Kaon B-parameter from quenched domain-wall QCD

We study the finite-temperature phase structure and the transition temperature of QCD with two flavors of dynamical quarks on a lattice with the temporal size