Eric Brittain Gregory

QCD thermodynamics with three flavors of improved staggered quarks

We report on a study of QCD thermodynamics with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad O(a{sup 2}) improved staggered quark action. Simulations were carried out with lattice spacings 1/4T, 1/6T, and 1/8T both for three degenerate quarks with masses less than or equal to the strange quark mass m{sub s} and for degenerate up and down quarks with masses in the range 0.1m{sub s}{<=}m{sub u,d}{<=}0.6m{sub s} and the strange quark mass fixed near its physical value. We present results for standard thermodynamics quantities, such as the Polyakov loop, the chiral order parameter and its susceptibility. For the quark masses studied to date we find a rapid crossover rather than a bona fide phase transition. We have carried out the first calculations of quark number susceptibilities with three flavors of sea quarks. These quantities are of physical interest because they are related to event-by-event fluctuations in heavy ion collision experiments. Comparison of susceptibilities at different lattice spacings show that our results are close to the continuum values.

Semileptonic decays of d mesons in three-flavor lattice QCD.

We present the first three-flavor lattice QCD calculations for D-->pilnu and D-->Klnu semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC Collaboration. With an improved staggered action for light quarks, we are able to simulate at light quark masses down to 1/8 of the strange mass. Consequently, the systematic error from the chiral extrapolation is much smaller than in previous calculations with Wilson-type light quarks. Our results for the form factors at q(2)=0 are f(D-->pi)(+)(0)=0.64(3)(6) and f(D-->K)(+)(0)=0.73(3)(7), where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the Cabibbo-Kobayashi-Maskawa matrix elements |V(cd)|=0.239(10)(24)(20) and |V(cs)|=0.969(39)(94)(24), where the last errors are from experimental uncertainties.

Semileptonic D→π/K and B→π/D decays in 2+1 flavor lattice QCD

We present results for form factors of semileptonic decays of D and B mesons in 2 + 1 flavor lattice QCD using the MILC gauge configurations. With an improved staggered action for light quarks, we successfully reduce the systematic error from the chiral extrapolation. The results for D decays are in agreement with experimental ones. The results for B decays are preliminary. Combining our results with experimental branching ratios, we then obtain the CKM matrix elements | V c d | , | V c s | , | V c b | and | v u b | . We also check CKM unitarity, for the first time, using only lattice QCD as the theoretical input.

First determination of the strange and light quark masses from full lattice QCD

We compute the strange quark mass

Lattice calculation of 1-+ hybrid mesons with improved Kogut-Susskind fermions

{m}_{s}

Topological susceptibility with the improved Asqtad action

and the average of the u and d quark masses

Pion and kaon physics with improved staggered quarks

\mathrm{m\ifmmode \hat{}\else \^{}\fi{}}

Exotic hybrid mesons from improved Kogut-Susskind fermions

using full lattice QCD with three dynamical quarks combined with the experimental values for the

High temperature QCD with three flavors of improved staggered quarks

\ensuremath{\pi}

Heavy-light meson decay constants withNf = 3

and K masses. The simulations have degenerate u and d quarks with masses