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

Abstract

We present an updated and improved extraction of the low-x gluon distribution from the HERA and LHCb exclusive J/ψ 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/ψ 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.

Working Group 5: Physics with Heavy Flavours

“…In addition, an analysis of exclusive J/ψ production has also been performed in Refs. [12,13]. A direct comparison of these results is not possible as the PDFs are extracted within a different theoretical framework, however an approximate transformation of the latter results allows for a comparison at the level of collinear PDFs and is shown in Fig.…”

Working Group 5: Physics with Heavy Flavours

“…In addition, an analysis of exclusive J/ψ production has also been performed in Refs. [12,13]. A direct comparison of these results is not possible as the PDFs are extracted within different theoretical frameworks, however an approximate transformation of the latter results allows for a comparison at the level of collinear PDFs and is shown in Fig.…”