Two-Flavor Simulations of ρ(770) and the Role of the KK[over ¯] Channel.

The ρ(770) meson is the most extensively studied resonance in lattice QCD simulations in two (N_{f}=2) and three (N_{f}=2+1) flavor formulations. We analyze N_{f}=2 lattice scattering data using unitarized chiral perturbation theory, allowing not only for the extrapolation in mass but also in flavor, N_{f}=2→N_{f}=2+1. The flavor extrapolation requires information from a global fit to ππ and πK phase shifts from experiment. While the chiral extrapolation of N_{f}=2 lattice data leads to masses of the ρ(770) meson far below the experimental one, we find that the missing KK[over ¯] channel is able to explain this discrepancy.