Multiplicity dependence of Ξ c⁺ and Ξ c⁰ production in pp collisions at √s=13 TeV

A bstract The first measurement at midrapidity (| y | < 0 . 5) of the production yield of the strange-charm baryons Ξ c⁺ and Ξ c⁰ as a function of transverse momentum ( p T ) in different charged-particle multiplicity classes in proton-proton collisions at √s=13 TeV with the ALICE experiment at the LHC is reported. The Ξ c⁺ baryon is reconstructed via the Ξ c⁺→ Ξ ⁻π ⁺π ⁺ decay channel in the range 4 < p T < 12 GeV /c , while the Ξ c⁰ baryon is reconstructed via both the Ξc⁰→ Ξ⁻π ⁺ and Ξc⁰→ Ξ⁻e⁺ν ₑ decay channels in the range 2 < p T < 12 GeV /c . The baryon-to-meson (Ξc0,+/D⁰) and the baryon-to-baryon (Ξc0,+/Λc⁺) production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at e + e − and e − p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of BR(Ξc⁰→ Ξ ⁻e⁺ν ₑ)/BR(Ξc⁰→ Ξ ⁻π ⁺) is measured as 0.825 ± 0.094 (stat.) ± 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.