Observation of a multiplicity dependence in the $p_{\mathrm{T}}$-differential charm baryon-to-meson ratios in proton-proton collisions at $\sqrt{s}=13$ TeV

Abstract

The production of prompt $D^0$, $D_{\mathrm{s}}^{+}$, and ${\Lambda }_{\mathrm{c}}^{+}$ hadrons, and their ratios, $D_{\mathrm{s}}^{+}$/$D^0$ and ${\Lambda }_{\mathrm{c}}^{+}$/$D^0$, are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV at midrapidity ($|y|<0.5$) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum ($p_{\mathrm{T}}$) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange $D_{\mathrm{s}}^{+}$/$D^0$ ratio indicates no significant multiplicity dependence, the baryon-to-meson $p_{\mathrm{T}}$-differential ${\Lambda }_{\mathrm{c}}^{+}$/$D^0$ ratio shows a multiplicity-dependent enhancement, with a significance of 5.3$\sigma$ for $1<p_{\mathrm{T}}<12$ GeV/$c$, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The ${\Lambda }_{\mathrm{c}}^{+}$/$D^0$ ratios as a function of $p_{\mathrm{T}}$ present a similar shape and magnitude as the $\Lambda /K_s^0$ ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The $p_{\mathrm{T}}$-integrated ratios, extrapolated down to $p_{\mathrm{T}}$=0, do not show a significant dependence on multiplicity within the uncertainties.

25 pages, 5 captioned figures, 1 table, authors from page 20, published version, figures at http://alice-publications.web.cern.ch/node/7524

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• Enhanced production of ${\Lambda }_b^0$ baryons in high-multiplicity $pp$ collisions at $\sqrt{s}=13$ TeV
• Charm and Bottom Hadrons in Hot Hadronic Matter
• Unveiling the effects of multiple soft partonic interactions in pp collisions at $\sqrt{\text{s}}=13.6$ TeV using charged-particle flattenicity
• Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s}=13$ TeV
• First measurement of ${\mathrm{\Omega }}_{\mathrm{c}}^0$ production in pp collisions at $\sqrt{s}=13$ TeV
• Measurement of beauty-strange meson production in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV via non-prompt ${{\mathrm{D}}_{\mathrm{s}}}^{+}$ mesons
• Towards the understanding of heavy quarks hadronization: from leptonic to heavy-ion collisions
• The study on the structure of exotic states ${\chi }_{c1}(3872)$ via beauty-hadron decays in $pp$ collisions at $\sqrt{s}=8\mathrm{TeV}$
• First measurement of prompt and non-prompt ${\mathrm{D}}^{\ast +}$ vector meson spin alignment in pp collisions at $\sqrt{s}=13$ TeV
• Azimuthal correlations of heavy-flavor hadron decay electrons with charged particles in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Measurement of the fraction of jet longitudinal momentum carried by ${\Lambda }_{\mathrm{c}}^{+}$ baryons in pp collisions
• Thermodynamical string fragmentation and string density effects in jets
• The Forward Physics Facility at the High-Luminosity LHC
• Multiplicity dependence of charm baryon and charm meson production in pPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV
• Charm fragmentation fractions and $\mathrm{c}\overline{\mathrm{c}}$ cross section in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Transverse momentum and multiplicity dependence of ${\Lambda }_c^{+}/D^0$ ratio in $pp$ collisions at $\sqrt{s}=13$ TeV
• Multiplicity, transverse momentum and pseudorapidity dependence of open-heavy flavored hadron production in proton+proton collisions at $\sqrt{s}$= 13 TeV using PYTHIA8
• Event-activity dependent production of strange and non-strange charmed baryons in the enhanced color-reconnection scheme
• Energy loss of heavy-flavor quarks in color string medium
• Studies of beauty hadron and non-prompt charm hadron production in pp collisions at $\sqrt{s}$=13 TeV within a transport model approach
• Measurement of the production cross section of prompt ${\Xi }_{\mathrm{c}}^0$ baryons in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• First measurement of ${\mathrm{D}}_{s1}(1^{+})(2536{)}^{+}$ and ${\mathrm{D}}_{s2}^{\ast }(2^{+})(2573{)}^{+}$ production in proton-proton collisions at $\sqrt{s}=13$ TeV at the LHC