No abstract

We extend our earlier lattice-QCD analysis of heavy-quark correlators to smaller lattice spacings and larger masses to obtain new values for the c mass and QCD coupling, and, for the first time, values for the b mass: m c ð3 GeV; n f ¼ 4Þ ¼ 0:986ð6Þ GeV, MS ðM Z ; n f ¼ 5Þ ¼ 0:1183ð7Þ, and m b ð10 GeV; n f ¼ 5Þ ¼ 3:617ð25Þ GeV. These are among the most accurate determinations by any method. We check our results using a nonperturbative determination of the mass ratio m b ð; n f Þ=m c ð; n f Þ; the two methods agree to within our 1% errors and taken together imply m b =m c ¼ 4:51ð4Þ. We also update our previous analysis of MS from Wilson loops to account for revised values for r 1 and r 1 =a, finding a new value MS ðM Z ; n f ¼ 5Þ ¼ 0:1184ð6Þ; and we update our recent values for light-quark masses from the ratio m c =m s . Finally, in the Appendix, we derive a procedure for simplifying and accelerating complicated least-squares fits.

We present a new lattice QCD analysis of heavy-quark pseudoscalar-pseudoscalar correlators, using gluon configurations from the MILC collaboration that include vacuum polarization from u, d, s and c quarks (n f = 4). We extract new values for the QCD coupling and for the c quark's MS mass: α MS (MZ , n f = 5) = 0.11822(74) and mc(3 GeV, n f = 4) = 0.9851(63) GeV. These agree well with our earlier simulations using n f = 3 sea quarks, vindicating the perturbative treatment of c quarks in that analysis. We also obtain a new nonperturbative result for the ratio of c and s quark masses: mc/ms = 11.652(65). This ratio implies ms(2 GeV, n f = 3) = 93.6(8) MeV when it is combined with our new c mass. Combining mc/ms with our earlier m b /mc gives m b /ms = 52.55(55), which is several standard deviations (but only 4%) away from the Georgi-Jarlskop prediction from certain GUTs. Finally we obtain an n f = 4 estimate for m b /mc = 4.528(54) which agrees well with our earlier n f = 3 result. The new ratio implies m b (m b , n f = 5) = 4.162(48) GeV.

We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (N f = 2 + 1 + 1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark masses is performed at two values of the lattice spacing a ≈ 0.078 fm and a ≈ 0.086 fm with lattice sizes ranging from L ≈ 1.9 fm to L ≈ 2.8 fm. We measure with high statistical precision the light pseudoscalar mass m PS and decay constant f PS in a range 270 m PS 510 MeV and determine the low energy parameters f 0 andl 3,4 of SU(2) chiral perturbation theory. We use the two values of the lattice spacing, several lattice sizes as well as different values of the light, strange and charm quark masses to explore the systematic effects. A first study of discretisation effects in light-quark observables and a comparison to N f = 2 results are performed.

We update our previous determination of both the decay constant and the mass of the Ds meson using the Highly Improved Staggered Quark formalism. We include additional results at two finer values of the lattice spacing along with improved determinations of the lattice spacing and improved tuning of the charm and strange quark masses. We obtain mD s = 1.9691(32) GeV, in good agreement with experiment, and fD s = 0.2480(25) GeV. Our result for fD s is 1.6σ lower than the most recent experimental average determined from the Ds leptonic decay rate and using Vcs from CKM unitarity. Combining our fD s with the experimental rate we obtain a direct determination of Vcs = 1.010(22), or alternatively 0.990 +0.013 −0.016 using a probability distribution for statistical errors for this quantity which vanishes above 1. We also include an accurate prediction of the decay constant of the ηc, fη c = 0.3947(24) GeV, as a calibration point for other lattice calculations.