Charm production and fragmentation fractions at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV

Measurements of the production cross sections of prompt D0, D+, D*+, ${D}_{s}^{+}$ , ${\Lambda }_{c}^{+}$ , and ${\Xi }_{c}^{+}$ charm hadrons at midrapidity in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum (p T) are provided with improved precision and granularity. The ratios of p T-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-x (10 −5–10 −4). The measurements of ${\Lambda }_{c}^{+}$ ( ${\Xi }_{c}^{+}$ ) baryon production extend the measured p T intervals down to p T = 0(3) GeV/c. These measurements are used to determine the charm-quark fragmentation fractions and the $c\overline{c}$ production cross section at midrapidity (|y| < 0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D0, D+, ${D}_{s}^{+}$ , ${\Lambda }_{c}^{+}$ , ${\Xi }_{c}^{0}$ and, for the first time, ${\Xi }_{c}^{+}$ , and of the strongly-decaying J/ψ mesons. The first measurements of ${\Xi }_{c}^{+}$ and ${\Sigma }_{c}^{0,++}$ fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e+e − and ep collisions. The $c\overline{c}$ production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations.