Investigating the Timelike Compton scattering in photon-proton interactions at the EIC

TL;DR

This paper explores timelike Compton scattering in electron-proton collisions at the future EIC to probe the three-dimensional structure of protons through GPDs, analyzing cross-sections, interference effects, and polarization asymmetries.

Contribution

It provides the first detailed predictions for TCS, BH, and interference contributions at the EIC, including polarized photon asymmetries, to aid future experimental GPD studies.

Findings

TCS and interference contributions are significant in the EIC kinematic range.

Photon circular polarization enhances the sensitivity to interference effects.

Results can help constrain GPD models through future measurements.

Abstract

Information about the 3-dimensional description of the quark and gluon content of hadrons, described by the generalized parton distributions (GPDs), can be probed by exclusive processes in electron - proton ($ep$) collisions. In this letter, we investigate the timelike Compton scattering (TCS) in $ep$ collisions at the future electron - ion collider (EIC). Such process is characterized by the exclusive dilepton production through the subprocess $\gamma p \rightarrow \gamma^*p \rightarrow l^+ l^- p$, with the real photon in the initial state being emitted by the incoming electron. Assuming a given model for the GPDs, the TCS differential cross-section is estimated, as well the contribution associated to the interference between the TCS and Bethe - Heitler (BH) amplitudes. Predictions for the TCS, BH and interference contributions are presented considering the kinematical range expected to be covered by the EIC detectors. Moreover, the polarized photon asymmetry is also studied. Our results indicated that a future experimental analysis, considering photon circular polarizations, can be useful to probe the interference contribution and constrain the description of the GPDs for the proton.