Probing chiral-even and chiral-odd leading twist quark generalized parton distributions through the exclusive photoproduction of a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi><mml:mi>ρ</mml:mi></mml:math> pair
G. Duplančić, Saad Nabeebaccus, K. Passek-Kumerički, B. Pire, L. Szymanowski, S. Wallon
Abstract
We extend our studies of a new class of $2\ensuremath{\rightarrow}3$ exclusive processes using the collinear factorization framework by considering the exclusive photoproduction of a $\ensuremath{\gamma}\ensuremath{\rho}$ pair, in the kinematics where the pair has a large invariant mass, and the outgoing $\ensuremath{\rho}$ meson has a sufficiently large transverse momentum to not resonate with the nucleon. We cover the whole kinematical range from medium energies in fixed-target experiments to very large energies of colliders, by considering the experimental conditions of JLab 12-GeV, COMPASS, and future EIC and LHC (in ultra-peripheral collisions) cases. One of the main interests in studying the present process is that it provides access to both chiral-even and chiral-odd generalized parton distributions, depending on the polarization of the outgoing $\ensuremath{\rho}$ meson, both at leading twist. Our analysis covers both neutral and charged $\ensuremath{\rho}$ mesons. We find that the orders of magnitude of the obtained cross sections are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab, for both longitudinally and transversely polarized $\ensuremath{\rho}$. Furthermore, we compute the linear photon beam polarization asymmetry which is sizable for a longitudinally polarized meson. These predictions are obtained for both the asymptotic distribution amplitude (DA) and the holographic DA.