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Exclusive photoproduction of a photon-meson pair: A new class of observables to probe GPDs

Duplančić, Goran; Nabeebaccus, Saad; Passek-Kumerički, Kornelija; Pire, Bernard; Schönleber, Jakob; Szymanowski, Lech; Wallon, Samuel (2024) Exclusive photoproduction of a photon-meson pair: A new class of observables to probe GPDs. Pos Proceedings of science . (Submitted)

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We discuss the exclusive photoproduction of a photon-meson pair with large pT as a channel to probe generalised parton distributions (GPDs). Like other 2→3 exclusive processes, this channel allows us to better study the x-dependence of GPDs, in contrast to 2→2 processes such as Deeply Virtual Compton Scattering (DVCS) which give only "moment-type" information. Moreover, it also gives the possibility to access, at leading twist, the chiral-odd GPDs, which are still completely unknown experimentally. In the first part of these proceedings, we present the computation of the amplitude at leading order and leading twist, for charged pions, and rho mesons of any charge and polarisation. These processes are sensitive to quark GPDs only. We also discuss the possibility of measuring such processes at various experiments, namely JLab, COMPASS, future EIC and LHC in ultra-peripheral collisions. In particular, in collider experiments, the dependence of GPDs at small skewness (<10−3) can be extracted. For the second part, we report on our recent work on the exclusive photoproduction of π0γ pair, which, in addition to a quark GPD channel, also has a contribution from gluon GPDs. In the latter case, we demonstrate that a collinear factorisation of the process fails, due to the presence of a Glauber pinch. Our findings also imply that other similar processes, like π0N→γγN also suffer from the same issue. On the other hand, we stress that the processes discussed earlier, which are sensitive to the quark GPD channels only, are safe from these factorisation breaking effects.

Item Type: Article
Additional Information: Imported from arXiv
Uncontrolled Keywords: QCD Phenomenology; Generalized Parton Distributions; Photon-Meson Pair; Photoproduction
Subjects: NATURAL SCIENCES > Physics > Physics of Elementary Particles and Fields
Divisions: Theoretical Physics Division
Project titleProject leaderProject codeProject type
Razotkrivanje strukture hadrona pomoću tvrdih ekskluzivnih procesa-REVESTRUCTUREKornelija Passek-KumeričkiIP-2019-04-9709HRZZ
Depositing User: Kornelija Passek-Kumerički
Date Deposited: 15 Feb 2024 13:35
DOI: 10.48550/arXiv.2401.17656

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