Scaling studies of QCD with the dynamical HISQ action

Abstract

We study the lattice spacing dependence, or scaling, of physical quantities using the highly improved staggered quark (HISQ) action introduced by the HPQCD/UKQCD collaboration, comparing our results to similar simulations with the asqtad fermion action. Results are based on calculations with lattice spacings approximately 0.15, 0.12 and 0.09 fm, using four flavors of dynamical HISQ quarks. The strange and charm quark masses are near their physical values, and the light-quark mass is set to 0.2 times the strange-quark mass. We look at the lattice spacing dependence of hadron masses, pseudoscalar meson decay constants, and the topological susceptibility. In addition to the commonly used determination of the lattice spacing through the static quark potential, we examine a determination proposed by the HPQCD collaboration that uses the decay constant of a fictitious "unmixed s bar s" pseudoscalar meson. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses.

36 pages, 11 figures, revised version to be published. Revisions include discussion of autocorrelations and several clarifications

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• Highly Improved Staggered Quarks on the Lattice, with Applications to Charm Physics
• High Precision determination of the pi, K, D and D_s decay constants from lattice QCD
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• Accelerating Staggered Fermion Dynamics with the Rational Hybrid Monte Carlo (RHMC) Algorithm
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• Computing K and D meson masses with N_f = 2+1+1 twisted mass lattice QCD
• Towards Four-Flavour Dynamical Simulations