Upsilon production in pp and pA collisions: from RHIC to the LHC

TL;DR

This paper reviews Upsilon production in proton-proton and proton-nucleus collisions across RHIC, Tevatron, and LHC energies, highlighting the agreement of Colour-Singlet Model predictions with experimental data and discussing nuclear effects.

Contribution

It demonstrates the accuracy of the Colour-Singlet Model in predicting Upsilon production and explores nuclear matter effects in various collision systems at high energies.

Findings

CSM predictions agree with LHC data at low transverse momentum

Upsilon cross-section ratios match recent LHC measurements

Gluon shadowing and EMC effects influence Upsilon production in nuclear collisions

Abstract

I discuss Upsilon production in pp collisions at RHIC, Tevatron and LHC energies, in particular the behaviour of the differential cross section in rapidity and the impact of QCD corrections on the P_T differential cross section. I also emphasise the very good agreement between the parameter-free predictions of the Colour-Singlet Model (CSM) and the first LHC data, especially in the region of low transverse momenta, which is the most relevant one for heavy-ion studies. I also show that the CSM predicts Upsilon cross-section ratios in agreement with the most recent LHC data. I then briefly discuss the nuclear-matter effects on Upsilon production at RHIC and the LHC in p(d)A collisions and, by extension, in AA collisions. I argue that a) the Upsilon break-up probability can be neglected, at RHIC and the LHC, b) gluon shadowing --although non-negligible-- is not strong enough to describe forward RHIC data, c) backward RHIC data hints at a gluon EMC effect, possibly stronger than the quark one. Outlooks for the LHC pPb run are also presented.