Measurement of Prompt D⁰, Λ_c⁺, and Σ_c^{0, ++} (2455) Production in Proton-Proton Collisions at √s = 13 TeV

The p_T-differential production cross sections of prompt D⁰, Λ_c⁺, and Σ_c^0,++(2455) charmed hadrons are measured at midrapidity (|y|<0.5) in pp collisions at √s=13 TeV. This is the first measurement of Σ_c^0,++ production in hadronic collisions. Assuming the same production yield for the three Σ_c^0,+,++ isospin states, the baryon-to-meson cross section ratios Σ_c^0,+,++/D⁰ and Λ_c⁺/D⁰ are calculated in the transverse momentum (p_T) intervals 2<p_T<12 and 1<p_T<24 GeV/c. Values significantly larger than in e⁺e^- collisions are observed, indicating for the first time that baryon enhancement in hadronic collisions also extends to the Σc. The feed-down contribution to Λc⁺ production from Σ_c^0,+,++ is also reported and is found to be larger than in e⁺e^- collisions. The data are compared with predictions from event generators and other phenomenological models, providing a sensitive test of the different charm-hadronization mechanisms implemented in the models.