Abstract
Exclusive photoproduction of a γπ± 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 αs 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 .
Highlights
Virtual Compton scattering (DVCS) and deeply virtual meson production [1,2,3,4,5,6] are the two main processes under study in order to extract the generalized parton distributions (GPDs), in particular at JLab and COMPASS
We studied the process γN → γπ±N ′ in the generalized Bjorken kinematics where GPD factorization is expected to hold in a collinear QCD approach
We restricted our analysis to unpolarized cross sections, which turn out to be large enough for the process to be analyzed in a quite detailed way by near-future experiments at JLab with photon beams originating from the 12 GeV electron beam
Summary
Virtual Compton scattering (DVCS) and deeply virtual meson production [1,2,3,4,5,6] are the two main processes under study in order to extract the generalized parton distributions (GPDs), in particular at JLab and COMPASS. Where (N, N ′) = (p, n) for the π+ case and (N, N ′) = (n, p) for the π− case In this process, a wide angle Compton scattering subprocess γ(qq) → γπ characterized by the large scale Mγπ (the invariant mass of the final state) factorizes from generalized parton distributions (GPDs). A wide angle Compton scattering subprocess γ(qq) → γπ characterized by the large scale Mγπ (the invariant mass of the final state) factorizes from generalized parton distributions (GPDs) One can relate this large scale Mγπ to the large transverse momenta transmitted to the final photon and to the final meson, the pair having an overall small transverse momentum. We describe several technical details required by analytical and numerical aspects of our study
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