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.
JHEP 10 (2023) 092
HEP Data
e-Print: arXiv:2302.07783 | PDF | inSPIRE
CERN-EP-2023-018
Figure group
Figure 1
Invariant-mass distribution of \Dzero candidates and their charge conjugates in selected \pt and multiplicity intervals. The blue solid curves show the total fit function and the red dashed curves show the combinatorial-background contribution. The green solid lines represent the reflection contribution. The raw-yield ($S$) values are reported together with their statistical uncertainties resulting from the fit. Top row: \Dzero mesons in the $2 < \pt < 4 \GeV/c$ interval for the low multiplicity class. Bottom row: \Dzero mesons in the $1 < \pt < 24 \GeV/c$ interval for the high multiplicity class. The corresponding BDT probability minimum threshold for the candidate selection is reported. The left (right) column corresponds to the prompt (non-prompt) \Dzero meson candidates dominated sample. |   |
Figure 2
Invariant-mass distribution of \Dplus candidates and their charge conjugates in selected \pt and multiplicity intervals. The blue solid curves show the total fit function and the red dashed curves show the combinatorial-background contribution. The raw-yield ($S$) values are reported together with their statistical uncertainties resulting from the fit. Top row: \Dplus mesons in the $2 < \pt < 4 \GeV/c$ interval for the low multiplicity class. Bottom row: \Dplus mesons in the $1 < \pt < 24 \GeV/c$ interval for the high multiplicity class. The corresponding BDT probability minimum threshold for the candidate selection is reported. The left (right) column corresponds to the prompt (non-prompt) \Dplus meson candidates dominated sample. |   |
Figure 3
Examples of raw-yield distribution as a function of the BDT-based selection employed in the $\chi^2$-minimisation procedure adopted for the determination of \fnonprompt of D mesons. Top row: \Dzero mesons in low multiplicity (left) and high multiplicity (right) classes. Bottom row: \Dplus mesons in low multiplicity (left) and high multiplicity (right) classes. |     |
Figure 4
Fractions of non-prompt \Dzero (left column) and \Dplus (right column) mesons as a function of \pt for the \inelgtrz class and the three multiplicity classes of events in pp collisions at $\s=13 \TeV$. The measurements are compared with the predictions obtained with \pythia and \epos event generators. |  |
Figure 5
Average fractions of non-prompt \Dzero and \Dplus mesons as a function of \pt for different multiplicity intervals normalised to the one measured in the \inelgtrz class of pp collisions at $\s=13 \TeV$. The measurements are compared with the predictions obtained with \pythia and \epos event generators and the \cgc model. |  |
Figure 6
Average fractions of non-prompt \Dzero and \Dplus mesons as a function of multiplicity, both normalised to the value corresponding to the \inelgtrz class, for pp collisions at $\s=13 \TeV$ in different \pt intervals and integrated in $1<\pt<24 \GeV/c$. The measurements are compared with predictions obtained with the \pythia and \epos event generators and the \cgc model . |  |
Figure 7
Fractions of non-prompt \Dzero (first row) and \Dplus (second row) mesons in $1<\pt<24 \GeV/c$ as a function of multiplicity for pp collisions at $\s=13 \TeV$ compared with predictions obtained with the \pythia event generator. The contributions from beauty meson and baryon decays in \pythia are displayed separately. |  |
