Exclusive electroproduction revisited: treating kinematical effects

TL;DR

This paper refines the theoretical description of exclusive real photon production by including exact kinematical effects and power-suppressed terms, improving the accuracy of generalized parton distribution extractions.

Contribution

It introduces a helicity formalism approach that incorporates exact kinematical effects and power-suppressed contributions in the analysis of exclusive leptoproduction processes.

Findings

Exact kinematical effects significantly impact cross section calculations.

Power-suppressed effects are essential for precise phenomenological analysis.

Helicity formalism provides a comprehensive framework for these corrections.

Abstract

Generalized parton distributions of the nucleon are accessed via exclusive leptoproduction of the real photon. While earlier analytical considerations of phenomenological observables were restricted to twist-three accuracy, i.e., taking into account only terms suppressed by a single power of the hard scale, in the present study we revisit this differential cross section within the helicity formalism and restore power-suppressed effects stemming from the process kinematics exactly. We restrict ourselves to the phenomenologically important case of lepton scattering off a longitudinally polarized nucleon, where the photon flips its helicity at most by one unit.