Charm production and fragmentation fractions at midrapidity in pp collisions at √s=13 TeV

Measurements of the production cross sections of prompt D-0, D+, D*(+), D-s(+), Lambda(+)(c), and Xi(+)(c) charm hadrons at midrapidity in proton-proton collisions at root 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 (c) over bar production cross section at midrapidity (|y| < 0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D-0, D+, D-s(+), Lambda(+)(c), Xi(0)(c) and, for the first time, Xi(+)(c), and of the strongly-decaying J/psi mesons. The first measurements of Xi(+)(c) and Sigma(0,++)(c) 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 (c) over bar production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations.