I. D. Kendall

The Upsilon spectrum and the determination of the lattice spacing from lattice QCD including charm quarks in the sea

eld congurations from the MILC collaboration. Using the 2 S 1S splitting to determine the lattice spacing, we are able to obtain the 1P 1S splitting to 1.4% and the 3S 1S splitting to 2.4%. Our improved result for M() M( b) is 70(9) MeV and we predict M( 0 ) M( 0) = 35(3) MeV. We also calculate ;K and s correlators using the Highly Improved Staggered Quark action and perform a chiral and continuum extrapolation to give values for M s (0.6893(12) GeV) and f s (0.1819(5) GeV) that allow us to tune the strange quark mass as well as providing an independent and consistent determination of the lattice spacing. Combining the NRQCD and HISQ analyses gives mb=ms = 54.7(2.5) and a value for the heavy quark potential parameter of r1 = 0.3209(26) fm.

Precise determination of the lattice spacing in full lattice QCD

We compare three different methods to determine the lattice spacing in lattice QCD and give results from calculations on the MILC ensembles of configurations that include the effect of u, d, and s sea quarks. It is useful, for ensemble to ensemble comparison, to express the results as giving a physical value for r{sub 1}, a parameter from the heavy quark potential. Combining the three methods gives a value for r{sub 1} in the continuum limit of 0.3133(23)(3) fm. Using the MILC values for r{sub 0}/r{sub 1}, this corresponds to a value for the r{sub 0} parameter of 0.4661(38) fm. One of our methods involves using the {eta}{sub s} to determine the lattice spacing and to tune the s-quark mass accurately. We give values for m{sub {eta}{sub s}}[0.6858(40) GeV] and f{sub {eta}{sub s}}[0.1815(10) GeV] needed to implement this. We show that the {eta}{sub s} method by itself is competitive with the r{sub 1} method on an ensemble by ensemble basis and compare the two.

Precise B, B_s, and B_c meson spectroscopy from full lattice QCD

We give the first accurate results for B and B{sub s} meson masses from lattice QCD including the effect of u, d, and s sea quarks, and we improve an earlier value for the B{sub c} meson mass. By using the highly improved staggered quark (HISQ) action for u/d, s, and c quarks and NRQCD for the b quarks, we are able to achieve an accuracy in the masses of around 10 MeV. Our results are: m{sub B}=5.291(18) GeV, m{sub B{sub s}}=5.363(11) GeV, and m{sub B{sub c}}=6.280(10) GeV. Note that all QCD parameters here are tuned from other calculations, so these are parameter free-tests of QCD against experiment. We also give scalar, B{sub s0}* and axial-vector, B{sub s1} meson masses. We find these to be slightly below threshold for decay to BK and B*K, respectively.

Update: Accurate Determinations of alpha_s from Realistic Lattice QCD

We obtain a new value for the QCD coupling constant by combining lattice QCD simulations with experimental data for hadron masses. Our lattice analysis is the first to (1) include vacuum polarization effects from all three light-quark flavors (using MILC configurations), (2) include third-order terms in perturbation theory, (3) systematically estimate fourth and higher-order terms, (4) use an unambiguous lattice spacing, and (5) use an [symbol: see text](a2)-accurate QCD action. We use 28 different (but related) short-distance quantities to obtain alpha((5)/(MS))(M(Z)) = 0.1170(12).

Update: Accurate Determinations of alpha(s) from Realistic Lattice QCD

We obtain a new value for the QCD coupling constant by combining lattice QCD simulations with experimental data for hadron masses. Our lattice analysis is the first to (1) include vacuum polarization effects from all three light-quark flavors (using MILC configurations), (2) include third-order terms in perturbation theory, (3) systematically estimate fourth and higher-order terms, (4) use an unambiguous lattice spacing, and (5) use an [symbol: see text](a2)-accurate QCD action. We use 28 different (but related) short-distance quantities to obtain alpha((5)/(MS))(M(Z)) = 0.1170(12).

Update: Accurate determinations ofαsfrom realistic lattice QCD

We obtain a new value for the QCD coupling constant by combining lattice QCD simulations with experimental data for hadron masses. Our lattice analysis is the first to (1) include vacuum polarization effects from all three light-quark flavors (using MILC configurations), (2) include third-order terms in perturbation theory, (3) systematically estimate fourth and higher-order terms, (4) use an unambiguous lattice spacing, and (5) use an [symbol: see text](a2)-accurate QCD action. We use 28 different (but related) short-distance quantities to obtain alpha((5)/(MS))(M(Z)) = 0.1170(12).