Studying charm hadronisation into baryons with azimuthal correlations of Λ c + with charged particles in pp collisions at s = 13 TeV

The distribution of angular correlations between prompt charm hadrons and primary charged particles in pp collisions is sensitive to the charm-quark hadronisation process. In this letter, charm-baryon correlations are measured for the first time by studying the azimuthal-angle difference between charged particles and prompt Λ c + baryons produced in pp collisions at a centre-of-mass energy of s = 13 TeV, with the ALICE detector. Λ c + baryons are reconstructed at midrapidity ( | y | < 0.5 ) in the transverse-momentum interval 3 < p T < 16 GeV/c, and correlated with charged particles with p T > 0.3 GeV/c and pseudorapidity | η | < 0.8 . For 3 < p T Λ c + , D < 5 GeV/c, the comparison with published measurements of D-meson and charged-particle correlations in the same collision system hints at a larger number of low-momentum particles associated with Λ c + -baryon triggers than with D-meson triggers, both in the collinear and opposite directions with respect to the trigger particle. These differences can be quantified by the comparison of the properties of the near- and away-side correlation peaks, and are not reproduced by predictions of various Monte Carlo event generators, generally underpredicting the associated particle yields at p T assoc < 1 GeV/c. This tension between Λ c + -baryon and D-meson associated peak yields could suggest a modified fragmentation of the charm quark, or a different hadronisation process, when a charm baryon is produced in the final state.. Authors: Acharya, S; Agarwal, A; Rinella, G Aglieri; Aglietta, L; Agnello, M. DOE Contract: AC02-05CH11231