Diffractive two-meson electroproduction with a nucleon and deuteron target

TL;DR

This paper explores how diffractive two-meson electroproduction processes can access generalized parton distributions, especially chiral-odd GPDs, on nucleon and deuteron targets, using collinear factorization in a high-energy regime.

Contribution

It provides a detailed analysis of various meson production channels and demonstrates the potential to probe GPDs in the ERBL region at future electron-ion colliders.

Findings

Cross sections are sensitive to GPD parameterizations.

Rates are within the reach of future electron-ion colliders.

Process enables access to chiral-odd transversity GPDs.

Abstract

The diffractive electro- or photo-production of two mesons separated by a large rapidity gap gives access to generalized parton distributions (GPDs) in a very specific way. First, these reactions allow to easily access the chiral-odd transversity quark GPDs by selecting one of the produced vector meson to be transversely polarized. Second, they are only sensitive to the so-called ERBL region where GPDs are not much constrained by forward quark distributions. Third, the skewness parameter $\xi$ is not related to the Bjorken $x_\text{Bj}$ variable, but to the size of the rapidity gap. We analyze different channels ($\rho_L^0\,\rho_{L/T}, \rho^0_L\,\omega_{L/T}$ and $\rho^0_L\,\pi$ production) on nucleon and deuteron targets. The analysis is performed in the kinematical domain where a large momentum transfer from the photon to the diffractively produced vector meson introduces a hard scale (the virtuality of the exchanged hard Pomeron). This enables the description of the hadronic part of the process in the framework of collinear factorization of GPDs. We show that the unpolarized cross sections depend very much on the parameterizations of both chiral-even and chiral-odd quark distributions of the nucleon, as well as on the shape of the meson distribution amplitudes. The rates are shown to be in the range of the capacities of a future electron-ion collider.