HEP Colloquia 2023

by Dr Carlo Flore (Università di Torino e INFN, Sezione di Torino)

Thursday 8 Jun 2023, 14:30 → 16:30 Europe/Rome

Sala Consiliare (Department of Physics)

Inclusive quarkonium photoproduction


Quarkonia are a perfect tool for testing QCD and hadronisation. Plenty of data from hadron-hadron and lepton-hadron colliders are available, but there is still a debate on the quarkonium production mechanism. Among different models for quarkonium production, the Colour Singlet Model (CSM), the Colour Evaporation Model (CEM), and the Non-Relativistic QCD (NRQCD) framework are the most used ones.

Within the NRQCD, a double expansion in $\alpha_s$ and in $v$, the heavy quark-antiquark pair relative velocity, is done, and the hadronisation of partons into a quarkonium is described in terms of Long-Distance Matrix Elements (LDMEs). Current LDME fits cannot describe at the same time the quarkonium production in different processes (as hadroproduction or photoproduction). To this extent, re-examining some of these processes in the CSM (that represents the leading-$v$ contribution of NRQCD) may be helpful for easing some of the issues currently faced in quarkonium physics.

In this talk, we present some recent studies on inclusive quarkonium photoproduction at lepton-hadron colliders at NLO in QCD in the CSM. First, we focus on transverse momentum differential cross sections for J/$\psi$ production. We show how, by properly accounting for some contributions as the feed-downs and the associated J/$\psi$+charm production, the photoproduction data from HERA can be described within the CSM. Then, we analyse the issue of negative integraded cross sections for inclusive quarkonium photoproduction at NLO in QCD. A solution to this problem is proposed, and predictions for future colliders such as the EIC and LHeC are given.