Charm-hadron production in \(pp\) and AA collisions

Abstract

Recent measurements of various charm-hadron ratios in \(pp\), \(p\)-Pb and Pb-Pb collisions at the LHC have posed challenges to the theoretical understanding of heavy-quark hadronization. The \(\Lambda_c/D^0\) ratio in \(pp\) and \(p\)-Pb collisions shows larger values than those found in \(e^+e^-\) and \(ep\) collisions and predicted by Monte-Carlo event generators based on string fragmentation, at both low and intermediate transverse momenta (\(p_T\)). In AA collisions, the \(D_s/D\) ratio is significantly enhanced over its values in \(pp\), while the \(\Lambda_c/D^0\) data indicates a further enhancement at intermediate \(p_T\). Here, we report on our recent developments for a comprehensive description of the charm hadrochemistry and transport in \(pp\) and \(AA\) collisions. For \(pp\) collisions we find that the discrepancy between the \(\Lambda_c/D^0\) data and model predictions is much reduced by using a statistical hadronization model augmented by a large set of "missing" states in the charm-baryon spectrum, contributing to the \(\Lambda_c\) via decay feeddown. For \(AA\) collisions, we develop a 4-momentum conserving resonance recombination model for charm-baryon formation implemented via event-by-event simulations that account for space-momentum correlations (SMCs) in transported charm- and thermal light-quark distributions. The SMCs, together with the augmented charm-baryon states, are found to play an important role in describing the baryon-to-meson enhancement at intermediate momenta. We emphasize the importance of satisfying the correct (relative) chemical equilibrium limit when computing the charm hadrochemistry and its momentum dependence with coalescence models.