Large-PT inclusive photoproduction of J/ψ in electron-proton collisions at HERA and the EIC

We study the inclusive J/psi production at large transverse momenta at lepton-hadron colliders in the limit when the exchange photon is quasi real, also referred to as photoproduction. Our computation includes the leading-P-T leading-nu next-to-leading alpha(s) corrections. In particular, we consider the contribution from J/psi plus another charm quark, by employing for the first time in quarkonium photoproduction the variable-flavour-number scheme. We also include a QED-induced contribution via an off-shell photon which remained ignored in the literature and which we show to be the leading contribution at high P-T within the reach of the EIC. In turn, we use our computation of J/psi + charm to demonstrate its observability at the future EIC and the EIC sensitivity to probe the non-perturbative charm content of the proton at high x. (C) 2020 The Authors. Published by Elsevier B.V.