Linking parton distributions to form factors and Compton scattering

Abstract

We relate ordinary and skewed parton distributions to soft overlap contributions to elastic form factors and large angle Compton scattering, using light-cone wave functions in a Fock state expansion of the nucleon. With a simple ansatz for the wave functions of the three lowest Fock states we achieve a good description of unpolarised and polarised parton distributions at large x, and of the data for the Dirac form factor and for Compton scattering, both of which can be saturated with soft contributions only. Large angle Compton scattering appears as a good case to investigate the relative importance of soft and hard contributions in exclusive processes which are sensitive to the end point regions of the nucleon wave function.

Compton-Scattering Cross Section on the Proton at High Momentum Transfer

“…Nevertheless, the experimental cross sections were at least 10 times larger than those predicted by perturbative QCD. More recently, calculations of RCS have been performed within a handbag dominance model [4,5], in which the external photons couple to a single quark, which couples to the spectator particles through generalized parton distributions (GPDs) [6]. These calculations are rather close to the Cornell cross section data.…”

Nucleon form factors from generalized parton distributions

“…Phenomenological estimates of the t-dependence and t-dependent parametrizations of GPDs have already been discussed in Refs. [10,13,[15][16][17][18][19], and more recently, in Ref. [20].…”

Exclusive Annihilationpp¯→γγin a Generalized Parton Picture

“…More recently, exclusive processes have been considered, which can be described in terms of generalized parton distributions, namely, deeply virtual Compton scattering (DVCS) and wide-angle real Compton scattering (WACS). It has been argued that at values of s few GeV 2 and jtj; juj s WACS is dominated by the soft mechanism [1,2]. The Compton scattering occurs off a single quark or antiquark in the nucleon.…”