Speaker
Description
Quarkonia are mesons formed of either a charm and anti-charm quark pair ($\rm{J}/\psi$, $\psi(2S)$), 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 and provide a reference baseline for p-A and A-A measurements. In p-A collisions these measurements quantify cold nuclear properties such as nuclear shadowing, gluon saturation, energy loss or break-up of the c\bar{c} pair in the medium. Disentangling cold nuclear effects from hot nuclear properties of the Quark-Gluon Plasma (QGP)is essential for the evaluation of the size of hot matter effects on charmonia in a QGP environment.
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 ($2.5 < y < 4$) $\rm{J}/\psi$ 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.
First Run-2 results on the J/$\psi$ and $\psi$(2S) production measurements in p-Pb collisions at sqrt{s_{\rm{NN}}}= 8.16 TeV, at forward and backward rapidities, will also be presented, together with new mid-rapidity J\psi results at sqrt{s_{\rm{NN}}}= 5.02 TeV. The J/$\psi$ and $\psi$(2S) nuclear modification factors will be compared to Run-1 results as well as theoretical calculations and will be interpreted in terms of cold nuclear matter effects.
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