Λ+c production in pp collisions at √s = 7 TeV and in p-Pb collisions at √sNN = 5.02 TeV

Abstract

The pT-di erential production cross section of prompt +c charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at p s = 7TeV and in p-Pb collisions at p sNN = 5:02TeV at midrapidity. The +c and { c were reconstructed in the hadronic decay modes +c ! pKð€€€ +, +c ! pK0 S and in the semileptonic channel +c ! e+ e (and charge conjugates). The measured values of the +c /D0 ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in di erent colliding systems, centre-of-mass energies, rapidity and pT intervals, where the +c production process may di er. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy- avour baryons is not well understood. The rst measurement at the LHC of the +c nuclear modi cation factor, RpPb, is also presented. The RpPb is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter e ects and a calculation that includes charm quark interactions with a decon ned medium.