Regular Article - Theoretical Physics
Curing the unphysical behaviour of NLO quarkonium production at the LHC and its relevance to constrain the gluon PDF at low scales
Université Paris-Saclay, CNRS, IJCLab, 91405, Orsay, France
Accepted: 17 May 2021
Published online: 5 June 2021
We address the unphysical energy dependence of quarkonium-hadroproduction cross sections at Next-to-Leading Order (NLO) in which we attribute to an over-subtraction in the factorisation of the collinear singularities inside the PDFs in the scheme. Such over- or under-subtractions have a limited phenomenological relevance in most of the scattering processes in particle physics. On the contrary, it is particularly harmful for -integrated charmonium hadroproduction which renders a wide class of NLO results essentially unusable. Indeed, in such processes, is not so small, the PDFs are not evolved much and can be rather flat for the corresponding momentum fractions and, finally, some process-dependent NLO pieces are either too small or too large. We propose a scale-fixing criterion which avoids such an over-subtraction. We demonstrate its efficiency for but also for a fictitious light elementary scalar boson. Having provided stable NLO predictions for -integrated cross sections, , and discussed the options to study hadroproduction, we argue that their measurement at the LHC can help better determine the gluon PDF at low scales and tell whether the local minimum in conventional NLO gluon PDFs around at scales below 2 GeV is physical or not.
© The Author(s) 2021
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