Quarkonia are mesons formed of either a charm and anti-charm quark pair (J/psi, psi(2S)), or a beauty and anti-beauty quark pair (Upsilon(1S), (2S) and (3S)). In high-energy hadronic collisions such as those delivered by the LHC between 2010 and 2016, quarkonium production results from the hard scattering of two gluons in a process which occurs very early in the collision followed by the hadronization of the heavy quark pair in a bound state. In pp collisions, quarkonium measurements help characterize production mechanisms. These same measurements also provide a reference baseline for p-A and A-A measurements which in turn quantify cold and hot nuclear properties of the Quark-Gluon Plasma (QGP). While charmonia are produced rather abundantly in such collisions, interpreting the measurement of their inclusive production is complicated by the presence of a sizable non-prompt contribution from the decay of b-hadrons. Bottomonia on the other hand have much smaller production cross sections but no non-prompt contribution. Moreover, their heavier mass makes them more suitable for perturbative QCD calculations.
In this presentation we will report on forward rapidity (2.5<y<4) J/psi and psi(2S) production measured in pp collisions at center of mass energies sqrt(s)=5.02 and 13 TeV, using data collected at the LHC in 2015. Together with similar measurements performed at sqrt(s)=2.76, 7 and 8 TeV, these results constitute a stringent test for models of charmonium production. In particular, they will be compared to NRQCD and FONLL calculations, which describe prompt and non-prompt charmonium production respectively. Results on forward-rapidity Upsilon production in pp collisions will also be discussed.
