Probing axial quark generalized parton distributions through exclusive photoproduction of a $γ\,π^\pm$ pair with a large invariant mass

Abstract

Exclusive photoproduction of a $γ\,π^\pm$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in $α_s$ and the differential cross sections for the process are estimated in the kinematics of the JLab~12-GeV experiments. The order of magnitude of the predicted cross-sections seems sufficient for a dedicated experiment to be performed. The process turns out to be very sensitive to the axial generalized parton distribution combination $\tilde{H}_u - \tilde{H}_d$.

44 pages, 16 figures. arXiv admin note: substantial text overlap with arXiv:1609.03830