1,139 research outputs found
Semileptonic Decays of Heavy Mesons with the Fat Clover Action
We are studying a variety of semileptonic decays of heavy-light mesons in an
effort to improve the determination of the heavy-quark Standard-Model CKM
matrix elements. Our fermion action is a novel, improved ``fat'' clover action
that promises to reduce problems with exceptional configurations. Dynamical sea
quarks are included in a mixed approach, i.e. we use staggered sea quarks and
fat-clover valence quarks. Here we report preliminary results.Comment: LATTICE99(heavyqk) - 3p, 4 Postscript fig
Chiral logs with staggered fermions
We compute chiral logarithms in the presence of "taste" symmetry breaking of
staggered fermions. The lagrangian of Lee and Sharpe is generalized and then
used to calculate the logs in and masses. We correct an error in Ref.
[1] [C. Bernard, hep-lat/0111051]; the issue turns out to have implications for
the comparison with simulations, even at tree level. MILC data with three light
dynamical flavors can be well fit by our formulas. However, two new chiral
parameters, which describe order hairpin diagrams for taste-nonsinglet
mesons, enter in the fits. To obtain precise results for the physical
coefficients at order , these new parameters will need to be bounded, at
least roughly.Comment: talk presented by C. Bernard at Lattice2002(spectrum); 3 pages, 2
figure
QCD thermodynamics with nonzero chemical potential at and effects from heavy quarks
We extend our work on QCD thermodynamics with 2+1 quark flavors at nonzero
chemical potential to finer lattices with . We study the equation of
state and other thermodynamic quantities, such as quark number densities and
susceptibilities, and compare them with our previous results at . We
also calculate the effects of the addition of the charm and bottom quarks on
the equation of state at zero and nonzero chemical potential. These effects are
important for cosmological studies of the early Universe.Comment: 27 pages, 17 figures. Some small text and figure change
Variants of fattening and flavor symmetry restoration
We study the effects of different "fat link" actions for Kogut-Susskind
quarks on flavor symmetry breaking. Our method is mostly empirical - we compute
the pion spectrum with different valence quark actions on common sets of sample
lattices. Different actions are compared, as best we can, at equivalent
physical points. We find significant reductions in flavor symmetry breaking
relative to the conventional or to the "link plus staple" actions, with a
reasonable cost in computer time. We also develop and test a scheme for
approximate unitarization of the fat links. While our tests have concentrated
on the valence quark action, our results will be useful in designing
simulations with dynamical quarks.Comment: 16 pages, LaTeX, PostScript figures include
Relativistic coupled-cluster studies of ionization potentials, lifetimes and polarizabilities in singly ionized calcium
Using the relativistic coupled-cluster method, we have calculated ionization
potentials, E1 matrix elements and dipole polarizabilities of many low-lying
states of Ca. Contributions from the Breit interaction are given explicitly
for these properties. Polarizabilities of the ground and the first excited
d-states are determined by evaluating the wave functions that are perturbed to
first order by the electric dipole operator and the black-body radiation shifts
are estimated from these results. We also report the results of branching
ratios and lifetimes of the first excited p-states using both the calculated
and experimental wavelengths and compare them with their measured values.Comment: 10 pages, 1 figur
Thermodynamics with 3 and 2+1 Flavors of Improved Staggered Quarks
We present preliminary results from exploring the phase diagram of finite
temperature QCD with three degenerate flavors and with two light flavors and
the mass of the third held approximately at the strange quark mass. We use an
order Symanzik improved gauge action and an order
improved staggered quark action. The improved staggered
action leads to a dispersion relation with diminished lattice artifacts, and
hence better thermodynamic properties. It decreases the flavor symmetry
breaking of staggered quarks substantially, and we estimate that at the
transition temperature for an to lattice {\em all} pions will
be lighter than the lightest kaon. Preliminary results on lattices with
, 6 and 8 are presented.Comment: 3 pages, 6 figures, contribution to Lattice2001(hightemp) August
19--24, 2001, Berlin, German
B meson form factors from HQET simulations
We use simulations of heavy quark effective field theory to calculate the
Isgur-Wise function, and we demonstrate the feasibility of calculating the
matrix element for the B \to \pi + \leptons decay in the lattice heavy quark
effective theory (HQET).Comment: 3 pages, 2 figures, talk presented at the lattice 97 conferenc
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