Measurement of beauty and charm production in pp collisions at $\sqrt{s} = 5.02$ TeV via non-prompt and prompt D mesons

The $p_{\rm T}$-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity ($|y| < 0.5$) in proton-proton collisions at $\sqrt{s} = 5.02$ TeV. The data sample used in the analysis corresponds to an integrated luminosity of ($19.3 \pm 0.4$) nb$^{-1}$. D mesons were reconstructed from their decays ${\rm D}^{0} \rightarrow {\rm K}^{-}\pi^{+}$, ${\rm D}^{+} \rightarrow {\rm K}^{-}\pi^{+}\pi^{+}$, and ${\rm D}_{\rm s}^{+} \rightarrow \phi\pi^{+} \rightarrow {\rm K}^{-}{\rm K}^{+}\pi^{+}$ and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt ${\rm D}^{+}$ and ${\rm D}_{\rm s}^{+}$ mesons have an extended $p_{\rm T}$ coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on $p_{\rm T}$, allowing for a more precise determination of their $p_{\rm T}$-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, $f_{\rm s}/(f_{\rm u} + f_{\rm d})$, is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The bb production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is ${\rm d}\sigma_{{\rm b\overline{b}}}/{\rm d}y|_{|y|< 0.5} = 34.5 \pm 2.4({\rm stat.}) \pm 2.5({\rm syst.}) \pm 0.7({\rm lumi.}) \pm 0.3({\rm BR}) ^{+3.8}_{-1}({\rm extr.}) \pm 0.5({\rm rap.shape})$ $\mu$b. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section predicted by perturbative QCD calculations.