Exclusive production of heavy quarkonia as a probe of the low x and low scale gluon PDF

Abstract

We discuss the exclusive $J/\psi$ photoproduction process, as measured recently at LHCb, as a means of constraining and ultimately determining the low $x$ and low $Q$ gluon PDF. The scale dependence of the theoretical prediction for this process is shown to be systematically improved via a taming of the known $\overline{\text{MS}}$ result, this amounts to resumming logarithmically enhanced small-$x$ terms and implementing a small-$Q$ power correction. The cross section level predictions allow the behaviour of the gluon PDF in the low $(x,Q)$ domain to be determined.

Comments: 4 pages, 3 figures. Proceedings of Light Cone 19 - QCD on the light cone: from hadrons to heavy ions (LC2019), submitted to PoS