$ρ$ Meson Decay in 2+1 Flavor Lattice QCD
We perform a lattice QCD study of the $ρ$ meson decay from the $N_f=2+1$ full QCD configurations generated with a renormalization group improved gauge action and a non-perturbatively $O(a)$-improved Wilson fermion action. The resonance parameters, the effective $ρ\toππ$ coupling constant and the resonance mass, are estimated from the $P$-wave scattering phase shift for the isospin I=1 two-pion system. The finite size formulas are employed to calculate the phase shift from the energy on the lattice. Our calculations are carried out at two quark masses, $m_π=410\,{\rm MeV}$ ($m_π/m_ρ=0.46$) and $m_π=300\,{\rm MeV}$ ($m_π/m_ρ=0.35$), on a $32^3\times 64$ ($La=2.9\,{\rm fm}$) lattice at the lattice spacing $a=0.091\,{\rm fm}$. We compare our results at these two quark masses with those given in the previous works using $N_f=2$ full QCD configurations and the experiment.