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Volume 297 - XXV International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2017) - WG1 and WG5 joint session
Probing the Low x Gluon with Exclusive $J/\psi$ Production
S. Jones,* A. Martin, M. Ryskin, T. Teubner
*corresponding author
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Pre-published on: 2017 October 21
Published on: 2018 January 16
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.
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