Unitary constraints on Deeply Virtual Compton Scattering

TL;DR

This paper demonstrates that unitarity constraints and a Regge pole approach can explain the large DVCS cross sections and asymmetries observed at JLab and Hermes without relying on GPDs, challenging traditional models.

Contribution

It introduces a unitarity-based method rooted in Regge theory to explain DVCS data, bypassing the need for generalized parton distributions.

Findings

Explains large DVCS cross sections at JLab.

Accounts for beam spin and charge asymmetries.

Provides a unitarity-based alternative to GPD models.

Abstract

At moderately low momentum transfer (-t up to 1 GeV^2) the coupling to the vector meson production channels gives the dominant contribution to real Compton and deeply virtual Compton scattering (DVCS). Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment explains not only the unexpectedly large DVCS unpolarized cross section that has been recently measured at Jefferson Laboratory (JLab), but also all the beam spin and charge asymmetries that has been measured at JLab and Hermes, without explicit need of Generalized Parton Distributions (GPD). The issue of the relationship between the two approaches is addressed.