Relatore
Descrizione
The production cross section of charm hadrons in hadronic collisions can be calculated using the factorisation approach as a convolution of three factors: the parton distribution functions (PDFs), the hard-scattering cross section at the partonic level, and the fragmentation functions of the produced heavy quarks into given species of heavy-flavour hadrons, which is assumed to be universal for different collision systems. However, recent observations of enhanced baryon-to-meson production yield ratios in hadronic collisions, with respect to the same measurements performed in $\rm e^{+}e^{-}$ or $\rm e^{-}$p collisions, suggest that the charm fragmentation fractions are not universal and depend on the collision system.
In this contribution, we present the measurements of $\rm D^{0}$, $\rm D^{+}$ and $\rm D^{+}_{\rm s}$ meson production, together with those of $\Lambda^{+}_{\rm c}$, $\Sigma^{0,++}_{\rm c}$, $\Xi^{0,+}_{\rm c}$ baryons, as well as the first result for $\Omega^{0}_{\rm c}$-baryon production at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE. These measurements confirm that the baryon-to-meson yield ratios in hadronic collisions are significantly larger than those measured in $\rm e^{+}e^{-}$ collisions, and are compared with different predictions assuming either in-vacuum fragmentation or modified hadronisation mechanisms for hadronic collisions.
Furthermore, the first measurement of the nuclear modification factor $R_{\rm pPb}$ for prompt $\Xi^{0}_{\rm c}$ baryons and non-prompt $\rm D^{0}$ mesons at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be shown. In p--Pb collisions, they provide important information about the cold nuclear matter (CNM) effects and help us understand how the possible presence of collectivity could influence the production of heavy-flavour hadrons. Finally, the measured charm fragmentation fractions and $c\overline{c}$ production cross section at midrapidity in pp collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be reported.
