Backward timelike Compton scattering to decipher the photon content of the nucleon

TL;DR

This paper investigates backward timelike Compton scattering to access the photon content of the nucleon, using collinear QCD factorization and Transition Distribution Amplitudes, with model estimates and cross section calculations.

Contribution

It introduces a novel approach to probe the photon content of the nucleon via TDAs in backward Compton scattering, providing theoretical estimates and analyzing background effects.

Findings

Model estimates of photon-to-nucleon TDAs are provided.

Cross sections for the process are calculated.

Background from Bethe-Heitler process is negligible.

Abstract

The exclusive photoproduction off nucleon of a large invariant mass lepton pair in the backward region specified by the small Mandelstam variable $-u$ is discussed in the framework of collinear QCD factorization. The amplitude is factorized in terms of photon-to-nucleon Transition Distribution Amplitudes (TDAs) which encode the photon content of the nucleon. Model estimates of these new non-perturbative objects are described and the corresponding cross sections calculated. The background due to the electromagnetic Bethe-Heitler process is shown to be negligible in the kinematical regime of interest.