Recent ALICE results on charm production and hadronisation

TL;DR

This paper reviews recent ALICE measurements of charm hadron production in pp, p--Pb, and Pb--Pb collisions, highlighting unexpected features that challenge existing hadronisation models and suggest non-universality of charm fragmentation.

Contribution

It presents new experimental results on charm hadron yields and ratios, and discusses their implications for understanding charm-quark hadronisation mechanisms at the LHC.

Findings

Charm fragmentation fractions may not be universal across collision systems.

The $ m ext{Λ}_c^+/ ext{D}^0$ ratio shows unexpected behavior in small and large systems.

Recombination and new colour reconnection mechanisms are important for modeling charm hadronisation.

Abstract

Studies on the production of open charm hadrons are of paramount importance to investigate the charm-quark hadronisation mechanisms at the LHC, particularly through the evolution of the production ratio between different charm-hadron species. Measurements performed in pp and p--Pb collisions at the LHC have revealed unexpected features, qualitatively similar to what observed in larger systems and, in the charm sector, not in line with the expectations based on previous measurements from $\rm e^{+}e^{-}$ colliders and in ep collisions. These results suggest that charm fragmentation fractions might not be universal and that the baryon-to-meson ratio depends on the collision system. Model calculations that better reproduce the $\Lambda_{\rm c}^{+}/{\rm D}^{0}$ ratio in pp collisions expect a significant contribution to $\Lambda_{\rm c}^{+}$ yield from decays of heavier charm-baryon states, rely on hadronisation via recombination mechanisms, or are based on new colour reconnection topologies. In this contribution, the most recent results on open heavy-flavour production in pp and Pb--Pb collisions measured by the ALICE Collaboration will be discussed. Emphasis will be given to the discussion of the impact of these studies on our understanding of the hadronisation processes.