Speaker
Description
We employ QCD collinear factorisation to compute the exclusive photoproduction of a photon-meson pair with a large invariant mass at leading order in the strong coupling $\alpha_s$ and at the leading twist. The mesons we consider are either rho mesons [1] or charged pions [2,3]. In particular, having a transversely-polarised rho meson in the final state allows for chiral-odd GPDs to be probed at the leading twist, which are not well-known experimentally. This process thus represents one of the few promising channels to measure them. We compute the various cross-sections and the linear polarisation asymmetries wrt the incoming photon. We also perform the phase space integrals to obtain estimations of counting rates at various experiments, namely at JLab-12-GeV, COMPASS, future EIC and LHC in ultra-peripheral collisions [3]. In particular, the high centre-of-mass energies available in collider experiments enables the study of GPDs at small skewness, a region where they are not well-known. Finally, we discuss our recent progress in the computation of NLO corrections in $\alpha_s$, as well as the computation of having a neutral pion in the final state, which probes gluonic GPDs as well.
[1] R. Boussarie, B. Pire, L. Szymanowski, and S. Wallon, “Exclusive photoproduction of a γ ρ pair with a large invariant mass,” JHEP 02 (2017) 054, arXiv:1609.03830 [hep-ph]. [Erratum: JHEP 10, 029 (2018)]
[2] G. Duplančić, K. Passek-Kumerički, B. Pire, L. Szymanowski, and S. Wallon, “Probing axial quark generalized parton distributions through exclusive photoproduction of a γ π ± pair with a large invariant mass,” JHEP 11 (2018) 179, arXiv:1809.08104 [hep-ph].
[3] G. Duplančić, S. Nabeebaccus, K. Passek-Kumerički, B. Pire, L. Szymanowski and S. Wallon, “Accessing GPDs through the exclusive photoproduction of a photon-meson pair with a large invariant mass,” [arXiv:2212.01034 [hep-ph]]
