Measurement of Prompt D$^{0}$, $\Lambda_{c}^{+}$, and $\Sigma_{c}^{0,++}$(2455) Production in Proton–Proton Collisions at $\sqrt s$ = 13 TeV

The $p_{\rm T}$-differential production cross sections of prompt D$^0$, Λ$_c^+$, and Σ$_c^{0,++}$(2455) charmed hadrons are measured at midrapidity (|y|<0.5) in pp collisions at $\sqrt{s}$=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$_c^{0,+,++}$/D$^0$ and Λ$_c^+$/D$^0$ are calculated in the transverse momentum ($p_\rm{T}$) intervals $2 < p_{\rm T} < 12$ and $1 < p_{\rm T} < 24$ 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 Σ$_c$. The feed-down contribution to Λ$_c^+$ 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.