2,771 research outputs found
Pion Form Factor in the Factorization Formalism
Based on the light-cone (LC) framework and the factorization formalism,
the transverse momentum effects and the different helicity components'
contributions to the pion form factor are recalculated. In
particular, the contribution to the pion form factor from the higher helicity
components (), which come from the spin-space Wigner
rotation, are analyzed in the soft and hard energy regions respectively. Our
results show that the right power behavior of the hard contribution from the
higher helicity components can only be obtained by fully keeping the
dependence in the hard amplitude, and that the dependence in LC wave
function affects the hard and soft contributions substantially. As an example,
we employ a model LC wave function to calculate the pion form factor and then
compare the numerical predictions with the experimental data. It is shown that
the soft contribution is less important at the intermediate energy region.Comment: 21 pages, 4 figure
The D234 action for light quarks
We investigate a new light fermion action (the ``D234'' action), which is
accurate up to \O(a^3) and tadpole-improved \O(a \alpha_s) errors. Using
D234 with Symanzik- and tadpole-improved glue we find evidence that continuum
results for the quenched hadron spectrum (pion, rho and nucleon) can be
obtained on coarse lattices.Comment: Latex, 4 pages, submitted to Lattice '95 proceeding
Flavor-Symmetry Restoration and Symanzik Improvement for Staggered Quarks
We resolve contradictions in the literature concerning the origins and size
of unphysical flavor-changing strong interactions generated by the
staggered-quark discretization of QCD. We show that the leading contributions
are tree-level in \order(a^2) and that they can be removed by adding three
correction terms to the link operator in the standard action. These corrections
are part of the systematic Symanzik improvement of the staggered-quark action.
We present a new improved action for staggered quarks that is accurate up to
errors of \order(a^4,a^2\alpha_s) --- more accurate than most, if not all,
other discretizations of light-quark dynamics.Comment: 7 page
P-wave meson properties with Wilson quarks
We describe two calculations involving P-wave mesons made of Wilson quarks:
the strong coupling constant in the presence of two flavors of light
dynamical fermions and the mass and decay constant of the meson.Comment: Poster presented at Lattice '94, September 27--October 1, 1994,
Bielefeld, Germany (no changes to manuscript, but correction of Authors list
above
and using NRQCD
This talk summarizes the quenched calculation of and
presented in hep-lat/9801038. The heavy quark is simulated using an
improved NRQCD action, and the tadpole improved clover action is used for the
light quarks. The axial current includes the corrections in one-loop
perturbation theory and the ones at tree-level. We discuss the
various systematic effects and consistency checks made in the calculation.Comment: 3 pages. Makefile and sources included. Talk presented at LATTICE98
(HEAVYQK
Quarkonium spin structure in lattice NRQCD
Numerical simulations of the quarkonium spin splittings are done in the
framework of lattice nonrelativistic quantum chromodynamics (NRQCD). At leading
order in the velocity expansion the spin splittings are of , where
is the renormalized quark mass and is the mean squared quark
velocity. A systematic analysis is done of all next-to-leading order
corrections. This includes the addition of relativistic
interactions, and the removal of discretization errors in the
leading-order interactions. Simulations are done for both S- and P-wave mesons,
with a variety of heavy quark actions and over a wide range of lattice
spacings. Two prescriptions for the tadpole improvement of the action are also
studied in detail: one using the measured value of the average plaquette, the
other using the mean link measured in Landau gauge. Next-to-leading order
interactions result in a very large reduction in the charmonium splittings,
down by about 60% from their values at leading order. There are further
indications that the velocity expansion may be poorly convergent for
charmonium. Prelimary results show a small correction to the hyperfine
splitting in the Upsilon system.Comment: 16 pages, REVTEX v3.1, 5 postscript figures include
- …