Lattice QCD ensembles with four flavors of highly improved staggered   quarks
  We present results from our simulations of quantum chromodynamics (QCD) with four flavors of quarks: u, d, s, and c. These simulations are performed with a one-loop Symanzik improved gauge action, and the highly improved staggered quark (HISQ) action. We are generating gauge configurations with four values of the lattice spacing ranging from 0.06 fm to 0.15 fm, and three values of the light quark mass, including the value for which the Goldstone pion mass is equal to the physical pion mass. We discuss simulation algorithms, scale setting, taste symmetry breaking, and the autocorrelations of various quantities. We also present results for the topological susceptibility which demonstrate the improvement of the HISQ configurations relative to those generated earlier with the asqtad improved staggered action. 
The MILC Collaboration: A. Bazavov, C. Bernard, C. DeTar, W. Freeman,   Steven Gottlieb, U. M. Heller, J. E. Hetrick, J. Kom...
hep-lat