First measurement of Lambda(+)(c) production down to p(T)=0 in pp and p-Pb collisions at root s(NN)=5.02 TeV

The production of prompt Lambda(+)(c) baryons has been measured at midrapidity in the transverse momentum interval 0 < pT < 1 GeV/c for the first time, in pp and p-Pb collisions at a center-of-mass energy per nucleon-nucleon collision root s(NN) = 5.02 TeV. The measurement was performed in the decay channel Lambda(+)(c) . pK0 S by applying new decay reconstruction techniques using a Kalman-Filter vertexing algorithm and adopting a machine-learning approach for the candidate selection. The pT -integrated Lambda(+)(c) production cross sections in both collision systems were determined and used along with the measured yields in Pb-Pb collisions to compute the pT -integrated nuclear modification factors RpPb and RAA of Lambda(+)(c) baryons, which are compared to model calculations that consider nuclear modification of the parton distribution functions. The Lambda(+)(c) /D0 baryon-to-meson yield ratio is reported for pp and p-Pb collisions. Comparisons with models that include modified hadronization processes are presented, and the implications of the results on the understanding of charm hadronization in hadronic collisions are discussed. A significant (3.7s) modification of the mean transverse momentum of Lambda(+)(c) baryons is seen in p-Pb collisions with respect to pp collisions, while the pT -integrated Lambda(+)(c) /D0 yield ratio was found to be consistent between the two collision systems within the uncertainties.

Automated summary

In this study, the production of prompt Lambda(+)(c) baryons was measured for the first time in pp and p-Pb collisions at a center-of-mass energy of 5.02 TeV, and new analysis techniques were applied. The obtained nuclear modification factors were compared with model calculations, and the implications of the results on charm hadronization were discussed.