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Hadronization is the process of formation of hadrons from quarks. This fundamental process in nature is governed by the strong force, which is described by the Quantum Chromo-Dynamics (QCD) theory of the Standard Model. Being realized by multiple soft processes, it is intrinsically not perturbative, therefore precise calculations are not possible. For this reason, hadronization is usually described via phenomenological approaches in “QCD inspired” models.
For years, state-of-the art QCD-based calculations at NLO and NLL order assumed that the transition from quarks to hadrons could be described using fragmentation functions, defined as the probability for a quark to produce a hadron of a given species carrying a fraction of the original quark momentum. These functions were tuned on e+e− collision data, and they have been used to calculate the production cross section of heavy-flavour hadrons in proton-proton collisions at ultra-relativistic energies, under the hypothesis of “universality” of the hadronization process. If these calculations describe the production of heavy-flavour mesons within uncertainties, they significantly underestimate the relative production of heavy-flavour baryons compared to that of mesons, challenging the concept of universal hadronization. Similarly, MC generators tuned to reproduce the charm-hadron production in e+e− collisions predict baryon-to-meson ratios in proton-proton collisions lower than those observed experimentally at the LHC.
In this contribution, an overview of the most recent experimental results of charm and beauty baryon production in pp and nuclear collisions at the LHC will be provided. The comparison with other collision systems (e+e–, Pb–Pb), as well as with novel theoretical models implementing different hadronization mechanisms will be also discussed.
Denise Piatti and Franco Galtarossa