Open charm production cross section from combined LHC experiments in $pp$ collisions at $\sqrt{s} = 5.02$ TeV
Open charm production in proton-proton collisions represents an important tool to investigate some of the most fundamental aspects of Quantum Chromodynamics, from the partonic mechanisms of heavy-quark production to the process of heavy-quark hadronisation. Over the last decade, the measurement of the production cross sections of charm mesons and baryons in proton-proton (pp) collisions was at the centre of a wide experimental effort at the Large Hadron Collider. Thanks to the complementarity of the different experiments, the production of charm hadrons was measured over a wide transverse momentum region and in different rapidity ranges. In this paper, the measurements of the charm hadrons $D^0$, $D^*$, $D^+$, $D_s^+$, $Λ_c^+$ and $Ξ_c^0$ performed by the ALICE, CMS and LHCb collaborations in pp collisions at the centre-of-mass energy $\sqrt{s}=\rm 5.02~TeV$ are combined to determine the total charm-quark production cross section $σ_{c\overline{c}}$ in a novel data-driven approach. The resulting total $c\overline{c}$ cross section is \begin{equation*} \begin{aligned} σ_\mathrm{c\overline{c}} (\mathrm{pp},5.02\,\mathrm{TeV}) ={} & 8340.9 \pm 217.8\mathrm{ (stat.) } {}^{+367.1}_{-367.2} \mathrm{ (syst.) } {}^{+362.5}_{-457.5} \mathrm{ (extr.) } + 679.9 (Ω_\mathrm{c})~μ\mathrm{b}. \end{aligned} \end{equation*} The measured charm-hadron distributions and corresponding cross sections are compared with the most recent theoretical calculations.