Lambda(+)(C) production in pb-pb collisions at root S-NN=5.02 TeV

Abstract

A measurement of the production of prompt Lambda(+)(C) baryons in Pb-Pb collisions at root S-NN = 5.02 TeV with the ALICE detector at the LHC is reported. The Lambda(+)(C) and (Lambda) over bar (-)(C) were reconstructed at midrapidity (vertical bar y vertical bar < 0.5) via the hadronic decay channel Lambda(+)(C) -> pK(S)(0) (and charge conjugate) in the transverse momentum and centrality intervals 6 < p(T) < 12 GeV/c and 0-80\%. The Lambda(+)(C)/D-0 ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at root s = 7 TeV and in p-Pb collisions at root S-NN = 5.02 TeV. In particular, the values in p-Pb and Pb-Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties in the common P-T interval covered by the measurements in the two collision systems. The Lambda(+)(C)/D-0 ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The Lambda(+)(C) nuclear modification factor, R-AA, is also presented. The measured values of the R-AA of Lambda(+)(C), D-S(+) and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy (R-AA(D0) < R-AA(DS+) < R-AA(Lambda C+)), conceivable with a contribution from coalescence mechanisms to charm hadron formation in the medium. (C) 2019 European Organization for Nuclear Research. Published by Elsevier B.V.