First measurement of Λc+ production down to pT=0 in pp and p -Pb collisions at sNN =5.02 TeV

Abstract

The production of prompt Λc+ 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 sNN=5.02TeV. The measurement was performed in the decay channel Λc+→pKS0 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 Λc+ 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 Λc+ baryons, which are compared to model calculations that consider nuclear modification of the parton distribution functions. The Λc+/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 (3.7σ) modification of the mean transverse momentum of Λc+ baryons is seen in p-Pb collisions with respect to pp collisions, while the pT-integrated Λc+/D0 yield ratio was found to be consistent between the two collision systems within the uncertainties. © 2023 CERN. for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.