Probing chiral-even and chiral-odd leading twist quark generalised parton distributions through the exclusive photoproduction of a $ \gamma \rho $ pair

• Main Authors: Duplančić, Goran, Nabeebaccus, Saad, Passek-Kumerički, Kornelija, Pire, Bernard, Szymanowski, Lech, Wallon, Samuel
• Format: Journal Article
• Language: English
• Published: 23.02.2023
• Subjects: Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology; Physics - Nuclear Experiment; Physics - Nuclear Theory
• DOI: 10.48550/arxiv.2302.12026

We extend our studies of a new class of $2 \to 3$ exclusive processes using the collinear factorisation framework by considering the exclusive photoproduction of a $\gamma\,\rho$ pair, in the kinematics where the pair has a large invariant mass, {and the outgoing $ \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, future EIC and LHC (in ultra-peripheral collisions) cases. One of the main interest in studying the present process is that it provides access to both chiral-even and chiral-odd GPDs, depending on the polarisation of the outgoing $\rho$-meson, both at leading twist. Our analysis covers both neutral and charged $ \rho $-mesons. We find that the order 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 polarised $\rho$. Furthermore, we compute the linear photon beam polarisation asymmetry {which is} sizeable for a longitudinally polarised meson. These predictions are obtained for both asymptotic distribution amplitude (DA) and the \textit{holographic} DA.