Studying charm hadronisation into baryons with azimuthal correlations of ${\Lambda }_{\mathrm{c}}^{+}$ with charged particles in pp collisions at $\sqrt{s}=13$ TeV

Abstract

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 ${\Lambda }_{\mathrm{c}}^{+}$ baryons produced in pp collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV, with the ALICE detector. ${\Lambda }_{\mathrm{c}}^{+}$ baryons are reconstructed at midrapidity ($|y|<0.5$) in the transverse-momentum interval $3<p_{\mathrm{T}}<16$ GeV/$c$, and correlated with charged particles with $p_{\mathrm{T}}>0.3$ GeV/$c$ and pseudorapidity $|\eta |<0.8$. For $3<p_{\mathrm{T}}^{{\Lambda }_{\mathrm{c}}^{+},\mathrm{D}}<5$ 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 ${\Lambda }_{\mathrm{c}}^{+}$-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 $p_{\mathrm{T}}^{\mathrm{assoc}}<1$ GeV/$c$. This tension between ${\Lambda }_{\mathrm{c}}^{+}$-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.

28 pages, 6 captioned figures, 1 table, authors from page 22, figures at http://alice-publications.web.cern.ch/node/11748