Wide angle Compton scattering on the proton: study of power suppressed corrections

TL;DR

This paper investigates wide angle Compton scattering on the proton using SCET, focusing on power suppressed corrections and their impact on cross sections and asymmetries, with phenomenological analysis and predictions for polarization observables.

Contribution

It provides a leading-order factorization formula including power corrections and nucleon helicity flip amplitudes within the SCET framework for wide angle Compton scattering.

Findings

Helicity flip amplitudes have a small contribution to the cross section.

The dominant contribution in the studied kinematic region is from the soft-spectator mechanism.

Predictions for double polarization observables are provided and compared with existing data.

Abstract

We study the wide angle Compton scattering process on a proton within the soft collinear factorization (SCET) framework. The main purpose of this work is to estimate the effect due to certain power suppressed corrections. We consider all possible kinematical power corrections and also include the subleading amplitudes describing the scattering with nucleon helicity flip. Under certain assumptions we present a leading-order factorization formula for these amplitudes which includes the hard- and soft-spectator contributions. We apply the formalism and perform a phenomenological analysis of the cross section and asymmetries in the wide angle Compton scattering on a proton. We assume that in the relevant kinematical region where $-t,-u>2.5$~GeV$^{2}$ the dominant contribution is provided by the soft-spectator mechanism. The hard coefficient functions of the corresponding SCET operators are taken in the leading-order approximation. The analysis of existing cross section data shows that the contribution of the helicity flip amplitudes to this observable is quite small and comparable with other expected theoretical uncertainties. We also show predictions for double polarization observables for which experimental information exists.