Hard probes in heavy ion collisions at the LHC: heavy flavour physics

TL;DR

Problem: quantify baseline heavy flavor and quarkonium production to disentangle quark-gluon plasma effects in heavy ion collisions at the LHC. Approach: combine NLO perturbative QCD for open heavy flavors with color evaporation model (and NRQCD comparisons) for quarkonia, and assess cold and hot nuclear matter effects, coalescence, and detector/MC tools. Key contributions: benchmark cross sections across pp, pA, and AA, analysis of shadowing, absorption, comover scattering, energy loss, and potential quarkonium regeneration, along with practical guidance for measurements by ALICE, CMS, and ATLAS. Significance: provides robust baselines and understanding of theoretical uncertainties to enable discrimination of QGP signals and to inform gluon nuclear PDFs and medium properties.

Abstract

We present the results from the heavy quarks and quarkonia working group. This report gives benchmark heavy quark and quarkonium cross sections for $pp$ and $pA$ collisions at the LHC against which the $AA$ rates can be compared in the study of the quark-gluon plasma. We also provide an assessment of the theoretical uncertainties in these benchmarks. We then discuss some of the cold matter effects on quarkonia production, including nuclear absorption, scattering by produced hadrons, and energy loss in the medium. Hot matter effects that could reduce the observed quarkonium rates such as color screening and thermal activation are then discussed. Possible quarkonium enhancement through coalescence of uncorrelated heavy quarks and antiquarks is also described. Finally, we discuss the capabilities of the LHC detectors to measure heavy quarks and quarkonia as well as the Monte Carlo generators used in the data analysis.