Revisiting NLO QCD corrections to total inclusive J/psi and Upsilon photoproduction cross sections in lepton-proton collisions

TL;DR

This paper reanalyzes NLO QCD corrections to J/psi and Upsilon photoproduction in lepton-proton collisions, addressing negative cross sections and proposing scale-fixing methods to improve predictions and gluon distribution insights.

Contribution

It introduces a scale-fixing criterion that resolves negative cross sections in NLO calculations across various collider energies.

Findings

Scale fixing successfully removes negative cross sections.

Method applicable from EicC to FCC-eh energies.

Potential to refine gluon content measurements at low scales.

Abstract

We revisit inclusive J/psi and Upsilon photoproduction at lepton-hadron colliders, namely in the limit when the exchanged photon is quasi real. Our computation includes the next-to-leading-order (NLO) alpha_s corrections to the leading-order contributions in v. Similarly to the case of NLO charmonium-hadroproduction processes, the resulting cross sections obtained in the MS-bar factorisation scheme are sometimes found to be negative. We show that the scale-fixing criteria which we derived in a previous study of eta(c) production successfully solves this problem from the EicC all the way up to the FCC-eh energies. We then elaborate on how to study a scale uncertainty akin to that derived by scale variations when one fixes a scale. In turn, we investigate where both J/psi and Upsilon photoproduction could be used to improve our knowledge of gluon content of the proton at scales as low as a couple of GeV.