Dergi makalesi Açık Erişim

production in Pb–Pb collisions at TeV

2019    CERN İşbirliği

A measurement of the production of prompt ${\Lambda }_{c}^{+}$ baryons in Pb–Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC is reported. The ${\Lambda }_{c}^{+}$ and ${{\stackrel{‾}{\Lambda }}_{c}}^{-}$ were reconstructed at midrapidity ($|y|<0.5$) via the hadronic decay channel ${\Lambda }_{c}^{+}\to p{K}_{S}^{0}$ (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 $\sqrt{s}=7$ TeV and in p–Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=5.02$ 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, ${R}_{\mathrm{AA}}$, is also presented. The measured values of the ${R}_{\mathrm{AA}}$ 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 $\left({R}_{\mathrm{AA}}^{{D}^{0}}<{R}_{\mathrm{AA}}^{{D}_{s}^{+}}<{R}_{\mathrm{AA}}^{{\Lambda }_{c}^{+}}\right)$, conceivable with a contribution from coalescence mechanisms to charm hadron formation in the medium.