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Hard exclusive photoproduction of photon-meson pairs: Pseudoscalar channels π, η, and η′

Nikola Crnković1,2, Goran Duplančić1, Saad Nabeebaccus3, Kornelija Passek-K.1, Bernard Pire4, Lech Szymanowski5, and Samuel Wallon6

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Phys. Rev. D 113, 034001 – Published 2 February, 2026

DOI: https://doi.org/10.1103/g9m4-9r9c

Abstract

We investigate the hard exclusive photoproduction of photon-meson pairs at leading twist and leading order in perturbative QCD and focus on pseudoscalar mesons M∈{π±,π0,η,η′}. Compact analytical expressions are obtained for the amplitudes involving quark generalized parton distributions, with the two-gluon components of the η and η′ distribution amplitudes included. The numerical analysis is performed in the moderate-ξ region, where valence-quark generalized parton distributions are expected to be important. In this region, we find a strong impact of the pion-pole term in γπ± production and a non-negligible effect for neutral mesons. We also observe a marked dependence of γη′ photoproduction on two-gluon contributions. This process offers enhanced sensitivity to the shape of the generalized parton distributions already at leading order, while the tested dependence on the meson distribution amplitude and the renormalization scale introduces further theoretical uncertainties, the latter emphasizing the need for next-to-leading-order corrections. Our results provide a concise analytical framework and a numerical baseline for future studies.

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Phys. Rev. D 113, 034001– Published 2 February, 2026
  • Received 24 November 2025
  • Accepted 16 December 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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