CERN Accelerating science

The production of prompt $\mathrm{\Lambda}_\mathrm{c}^+$ hadrons at midrapidity $|y|<0.5$ in proton-proton collisions at $\sqrt{\mathrm{s}} = 13$ as a function of charged-particle multiplicity is presented. Also analogous measurements of $\mathrm{D}^0$ and $\mathrm{D}_\mathrm{s}^+$ production are currently being carried out and the $\mathrm{D}_\mathrm{s}^+ / \mathrm{D}^0$ as well as the $\mathrm{\Lambda}_\mathrm{c}^+/ \mathrm{D}^0$ production ratios are discussed. In contrast to the $\mathrm{D}_\mathrm{s}^+ / \mathrm{D}^0$ production ratio, the $\mathrm{\Lambda}_\mathrm{c}^+ / \mathrm{D}^0$ production ratio shows an increase with increasing multiplicity. In addition, its ratio is significantly underestimated by predictions where fragmentation is tuned to $\mathrm{e}^+\mathrm{e}^-$ and $\mathrm{e}^-\mathrm{p}$ measurements. On the other hand, comparisons with a canonical approach of a statistical hadronisation model with augmented baryon production as well as with a fragmentation model implementing colour reconnection beyond leading colour approximation are shown to qualitatively describe the shape and multiplicity dependence. The $\mathrm{\Lambda}_\mathrm{c}^+ / \mathrm{D}^0$ ratio is similar in shape and magnitude compared to the light-flavour ratio $\mathrm{\Lambda} / \mathrm{K}_\mathrm{S}^0$ measured at comparable multiplicities. Together, these results indicate (i) hadronisation mechanisms beyond pure in-vacuum fragmentation in $\mathrm{p}\mathrm{p}$ collisions as well as (ii) potential common mechanisms of baryon formation in the light-flavour and heavy-flavour sector. The Virtual Monte Carlo (VMC) detector simulation framework which is used by the ALICE and FAIR collaboration has been extended to support track partitioning among multiple different simulation engines. Before, it was only possible to use one chosen engine for the entire event simulation. Especially in view of the coming LHC Run 3 and 4, faster simulations are crucial to cope with the expected increase of experimental data. The enhanced VMC framework is now capable of running full-simulation together with fast-simulation. Based on specified user conditions, the simulation of single tracks can be transferred from full-simulations to be handled by fast-simulations when feasible to speed-up the detector simulation.