Accessing baryon-antibaryon generalized distribution amplitudes in $e^{\pm} \gamma \to e^{\pm} B \bar{B} $

Abstract

$\gamma^* \gamma \to B \bar{B}$ is the golden process to access chiral-even di-baryon generalized distribution amplitudes (GDAs) as deeply virtual Compton scattering has proven to be for the generalized parton distributions. In the framework of colinear QCD factorization where the leading twist amplitude is the convolution of GDAs and a perturbatively calculable coefficient function, we study the scattering amplitude for the baryonic channels where $B$ is a spin $1/2$ baryon such as the nucleon or hyperon $\Lambda, \Sigma$. Taking into account the interfering QED amplitude, we calculate the cross section of the $e^\pm \gamma \to e^\pm B \bar B$ process that can be experimentally studied in $e^- e^+$ as well as in electron-ion facilities. We explore both the final state polarization summed case and the polarization dependent effects. Numerical estimates are presented for $e^- \gamma \to e^- p \bar{p}$, using motivated models for GDAs. Our results show that a first extraction of baryon-antibaryon GDAs from experimental measurements is feasible at Belle II.