Single and double polarization observables in timelike Compton scattering off proton

TL;DR

This paper investigates the photoproduction of lepton pairs off protons to explore proton quark structure using GPDs, deriving amplitudes and calculating various spin observables in the valence region.

Contribution

It provides a detailed derivation of amplitudes and comprehensive calculations of polarization observables for timelike Compton scattering using GPD formalism.

Findings

Calculated unpolarized, single- and double-spin observables

Expressed observables in terms of GPDs

Enhanced understanding of proton structure in valence region

Abstract

We study the exclusive photoproduction of a lepton pair off the proton with the aim of studying the proton quark structure via the Generalized Parton Distributions (GPD) formalism. After deriving the amplitudes of the processes contributing to the $\gamma P\to P' e^+e^-$, the Timelike Compton Scattering and the Bethe-Heitler process, we calculate all unpolarized, single- and double- beam-target spin observables in the valence region in terms of GPDs.