Measurement of the non-prompt D-meson fraction as a function of multiplicity in proton$-$proton collisions at $\sqrt{s} = 13$ TeV

TL;DR

This study measures the fraction of non-prompt D mesons from beauty-hadron decays in proton-proton collisions at 13 TeV, finding a slight increase with transverse momentum but no significant dependence on event multiplicity, and compares results with various models.

Contribution

It provides the first detailed measurement of non-prompt D-meson fractions as a function of multiplicity at 13 TeV, testing charm and beauty quark production models.

Findings

Non-prompt D-meson fraction increases with transverse momentum.

No significant dependence of non-prompt fraction on charged-particle multiplicity.

Results are consistent with certain Monte Carlo and theoretical models.

Abstract

The fractions of non-prompt (i.e. originating from beauty-hadron decays) D$^0$ and D$^+$ mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton$-$proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum ($p_{\rm T}$) and integrated in the range $1 < p_{\rm T} < 24$ GeV/$c$. The fraction of non-prompt D$^0$ and D$^+$ mesons is found to increase slightly as a function of $p_{\rm T}$ in all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion.