Light-Front Dynamics and Generalized Parton Distributions

Abstract

In this work we report on using light-front dynamics to describe generalized parton distributions, which are correlation functions encountered in virtual Compton scattering at large momentum transfer. This two photon process requires pair annihilation contributions which are subtle to handle in light-front dynamics. We are careful to derive such contributions in the light-front Bethe-Salpeter formalism. This derivation highlights the connection to the Fock space picture as well as provides a toy model for generalized parton distributions.Ultimately we use light-front dynamics to build a phenomenological parametrization for the proton's generalized parton distributions. This task is non-trivial due to the field theoretic constraints required of these distributions. To meet the constraints imposed by Lorentz covariance, we approach generalized parton distributions from the perspective of double distributions. Despite avid phenomenological use, surprisingly little work has been done to calculate double distributions. We first focus on a number of simple pedagogical examples and demonstrate how double distributions can be correctly determined. The double distributions we derive, including those for the proton, satisfy known constraints and are adequate for phenomenological estimates of cross sections. The models used allow one to study the interplay between the light-front formulation and Lorentz covariance.