Rho resonance parameters from lattice QCD

We perform a high-precision calculation of the phase shifts for p-p scattering in the I = 1, J = 1 channel in the elastic region using elongated lattices with two mass-degenerate quark flavors (N-f = 2). We extract the rho resonance parameters using a Breit-Wigner fit at two different quark masses, corresponding to m(pi) = 226 MeV and m(pi) = 315 MeV, and perform an extrapolation to the physical point. The extrapolation is based on a unitarized chiral perturbation theory model that describes well the phase shifts around the resonance for both quark masses. We find that the extrapolated value, m(rho) = 720(1)(15) MeV, is significantly lower that the physical rho mass and we argue that this shift could be due to the absence of the strange quark in our calculation.