Chiral properties of light mesons with $N_f=2+1$ overlap fermions

We present an update of the light meson spectrum with $N_f$=2+1 overlap fermions on a $16^3times 48$ lattice at five different up and down quark masses and two strange quark masses. Based on our experience with the previous simulation with $N_f=2$, we carry out the chiral extrapolation with the prediction of the chiral perturbation theory at the next-to-next-to leading order. We also check the consistency of our analysis by using alternative chiral extrapolation with a reduced theory in which the strange quark mass is integrated out.

Non-perturbative renormalization of bilinear operators with dynamical overlap fermions

Using the non-perturbative renormalization technique, we calculate the renormalization factors for quark bilinear operators made of overlap fermions on the lattice. The background gauge field is generated by the JLQCD and TWQCD collaborations including dynamical effects of two or 2+1 flavors of light quarks on a 16$^3times$32 or 16$^3times$48 lattice at lattice spacing around 0.1 fm. By reducing the quark mass close to the chiral limit, where the finite volume system enters the so-called $epsilon$-regime, the unwanted effect of spontaneous chiral symmetry breaking on the renormalization factors is suppressed. On the lattices in the conventional $p$-regime, this effect is precisely subtracted by separately calculating the contributions from the chiral condensate.

Light meson spectrum with $N_f=2+1$ dynamical overlap fermions

We report on a numerical simulation with 2+1 dynamical flavors of overlap fermions. We calculate pseudo-scalar masses and decay constants on a $16^3times 48 times (0.11 {rm fm})^4$ lattice at five different up and down quark masses and two strange quark masses. The lightest pion mass corresponds to $approx 310$ MeV. We also study the validity of the chiral perturbation theory using the results of the numerical simulation with two dynamical flavors and conclude that the one-loop formulae cannot be directly applied in the strange quark mass region. We therefore extrapolate our 2+1-flavor results to the chiral limit by fitting the data to the two-loop formulae of the chiral perturbation theory.

Light meson spectrum with $N_f=2$ dynamical overlap fermions

We present numerical simulation of QCD with two dynamical quark flavors described by the overlap fermion action on a $16^3times 32times (0.12 {rm fm})^4$ lattice. We calculate pseudo-scalar masses and decay constants and investigate their chiral properties. We test the consistency of our data with the two-loop chiral perturbation theory predictions, which should also be valid at finite lattice spacings because of the exact chiral symmetry, including the finite size effects.