Pion Form Factors at Intermediate Momentum Transfer in a Covariant Approach

We study the pion electromagnetic and $\gamma^* + \pi^0 \to \gamma$ transition form factors at intermediate momentum transfer. We calculate soft, nonperturbative corrections to the leading perturbative amplitudes which arise from the $q\bar q$-component of the pion wave function. We work in Minkowski space and use a Lorentz covariant, gauge-invariant generalized perturbative integral representation for the $q\bar q$ amplitudes. For the transition form factor we find relative insensitivity to the detailed nonperturbative structure of the wavefunction for |q^2|\gsim 10~GeV$^2$, 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 π+π−\pi^+\pi^- photoproduction

Assuming that the $\pi^+\pi^-$ photoproduction at forward angles and high energies is dominated by one pion exchange we calculate the $\pi^+\pi^-$ mass distributions for low partial waves. Predictions of the model agree well Assuming that the $\pi^+\pi^-$ photoproduction at forward angles and high energies is dominated by one pion exchange we calculate the $\pi^+\pi^-$ mass distributions for low partial waves. Predictions of the model agree well with the experimental data which indicate that the $S$, $P$ and $D$ waves are dominated by the $f_0(980)$, $\rho(770)$ and $f_2(1270)$, resonances respectively.Comment: 6 pages, 7 figure