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Probing the Low x Gluon with Exclusive $J/\psi$ Production

S. Jones, A. Martin, M. Ryskin, T. Teubner

in XXV International Workshop on Deep-Inelastic Scattering and Related Subjects

Contribution: pdf


We present an updated and improved extraction of the low-$x$ gluon distribution from the HERA and LHCb exclusive $J/\psi$ production data in the context of $k_T$ factorisation. Critically, we use a more precise expression for the photon flux and updated rapidity gap survival factors.

In collinear factorisation, exclusive $J/\psi$ photoproduction receives large perturbative corrections at next-to-leading order which depend sensitively on the factorisation scale. This prevents the use of the available data to extract a gluon PDF within this framework. Attempts to understand and overcome the problems caused by the large perturbative corrections are discussed.