988 research outputs found
Pion Form Factors at Intermediate Momentum Transfer in a Covariant Approach
We study the pion electromagnetic and
transition form factors at intermediate momentum transfer. We calculate soft,
nonperturbative corrections to the leading perturbative amplitudes which arise
from the -component of the pion wave function. We work in Minkowski
space and use a Lorentz covariant, gauge-invariant generalized perturbative
integral representation for the amplitudes. For the transition form
factor we find relative insensitivity to the detailed nonperturbative structure
of the wavefunction for |q^2|\gsim 10~GeV, whereas considerable
sensitivity is found for the electromagnetic form factor.Comment: 21 pages, REVTeX 3.0 file, (uuencoded postscript files of 10 figures
appended), ADP-93-216/T13
What is Measured in Hard Exclusive Electroproduction?
We examine the relation between amplitudes measured in exclusive
lepto-production and the quark content of the nucleon. We show that in the
limit of high energy and small t, the natural interpretation of amplitudes
measured in these hard exclusive processes is in terms of the quark content of
the meson cloud and not the target itself. In this regime, Regge amplitudes
will make a significant contribution to these exclusive amplitudes. This leads
to violation of QCD scaling.Comment: 6 pages, 2 figure
Constructing Confinement
The interaction between static quarks is derived by applying many-body
techniques to QCD in Coulomb gauge. The result is shown to be exact in the IR
and UV limits, and agrees remarkably well with lattice computations.Comment: 6 pages, 3 figures, proceedings for 2002 Lake Louise Winter Institut
Separation of Soft and Hard Physics in DVCS
A model for deeply virtual Compton scattering, based on analytical light-cone
hadron wave functions is presented and studied at energies currently accessible
at Jefferson Laboratory and DESY. It is shown that poles and perpendicular
vector components play an important role at Q^2 < 10 GeV^2. A Q^2 suppressed
diagram has to be included at these low energies, but becomes negligible above
10 GeV^2. Future prospects and developments of this model are discussed.Comment: 6 pages, 2 figures, uses ws-procs9x6.cls, to appear in Proceedings of
the Exclusive Processes at High-t Workshop at Jefferson Lab, May 15-18 200
Meson resonances in forward-angle photoproduction
Assuming that the photoproduction at forward angles and high
energies is dominated by one pion exchange we calculate the mass
distributions for low partial waves. Predictions of the model agree well
Assuming that the photoproduction at forward angles and high
energies is dominated by one pion exchange we calculate the mass
distributions for low partial waves. Predictions of the model agree well with
the experimental data which indicate that the , and waves are
dominated by the , and , resonances
respectively.Comment: 6 pages, 7 figure
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