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Wide-angle photoproduction of the η′-meson and its gluon content

We investigate wide-angle photoproduction of the η′ meson within the handbag approach to twist-3 accuracy. It turns out that, due to the gluon content of the η ′, this process is dominated by twist 2 in contrast with pion and η photoproduction. Using the presently avail- able information on the twist-2 and twist-3 distribution amplitudes and on the η − η ′ mixing, we provide prediction for ′ the η′ cross sec- tion and helicity correlations. It is argued that η photoproduction is well suited to improve our knowledge of the two-gluon distribution amplitude.

exclusive processes ; meson photoproduction ; wide-angle ; eta'-meson, higher-twist

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