Wide-angle photoproduction of the ${\eta }^{\mathrm{\prime }}$-meson and its gluon content

We investigate wide-angle photoproduction of the ${\eta }^{\mathrm{\prime }}$ meson within the handbag approach to twist-3 accuracy. It turns out that, due to the gluon content of the ${\eta }^{\mathrm{\prime }}$, this process is dominated by twist-2 in contrast with pion and $\eta$ photoproduction. Using the presently available information on the twist-2 and twist-3 distribution amplitudes and on the $\eta -{\eta }^{\mathrm{\prime }}$ mixing, we provide prediction for the ${\eta }^{\mathrm{\prime }}$ cross section and helicity correlations. It is argued that ${\eta }^{\mathrm{\prime }}$ photoproduction is well suited to improve our knowledge of the two-gluon distribution amplitude.