Chiral and continuum extrapolation of partially-quenched lattice results

Abstract

The vector meson mass is extracted from a large sample of partially quenched, two-flavor lattice QCD simulations. For the first time, discretisation, finite-volume and partial quenching artefacts are treated in a unified framework which is consistent with the low-energy behaviour of QCD. This analysis incorporates the leading infrared behaviour dictated by chiral effective field theory. As the two-pion decay channel cannot be described by a low-energy expansion alone, a highly-constrained model for the decay channel of the rho-meson is introduced. The latter is essential for extrapolating lattice results from the quark-mass regime where the rho is observed to be a physical bound state.Recent developments in lattice QCD have enabled the first large-scale simulation of chiral, dynamical fermions [1]. While this accomplishment is a significant milestone in the progress towards an accurate description of physical QCD, the high demand on computing resources restricts practical calculations to an unphysical domain of simulation parameters. In particular, lattice QCD involves a discretised space-time of finite spatial extent, with input quark masses much larger than those in Nature. Each of these approximations requires special attention in the extraction of physical observables from Monte Carlo simulations. In this Letter we analyse a very large set of partially quenched data for the mass of the ρ meson. We show that a systematic analysis of this data enables us to remove the effects of partial quenching and to take both the continuum and infinite volume limits. The resulting data lies on a single, well defined curve which extrapolates to a value within ∼1% of the physical ρ mass. The contrast between the raw lattice data (note the scatter in Fig. 2) and the corrected data shown in Fig. 3 is striking.

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