Observation of a multiplicity dependence in the pT-differential charm baryon-to-meson ratios in proton-proton collisions at √s=13 TeV

The production of prompt D-0, D-s(+) and Lambda(+)(c) hadrons, and their ratios, D-s(+)/D-0 and Lambda(+)(c)/D-0, are measured in proton-proton collisions at root s = 13 TeV at midrapidity (vertical bar y vertical bar < 0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (p(T)) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange D-s(+)/D-0 ratio indicates no significant multiplicity dependence, the baryon-to-meson P-T-differential Lambda(+)(c)/D-0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3 sigma for 1 < p(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(+)(c)/D-0 ratios as a function of p(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 charmhadron formation, with analogous multiplicity dependence. The p(T)-integrated ratios, extrapolated down to p(T) = 0, do not show a significant dependence on multiplicity within the uncertainties. (C) 2022 European Organization for Nuclear Research. Published by Elsevier B.V.

Automated summary

The production of prompt D-0, D-s(+) and Lambda(+)(c) hadrons and their ratios were measured in proton-proton collisions at 13 TeV using the ALICE detector at the LHC. The study found a multiplicity-dependent enhancement in the baryon-to-meson P-T-differential Lambda(+)(c)/D-0 ratio, while the strange to non-strange D-s(+)/D-0 ratio showed no significant multiplicity dependence. The results were compared with theoretical models and event generators, suggesting a potential common mechanism for light- and charm-hadron formation.