Studying charm hadronisation into baryons with azimuthal correlations of $\Lambda_{\rm c}^{+}$ with charged particles in pp collisions at $\mathbf{\sqrt{\it s} = 13}$ TeV

TL;DR

This study measures azimuthal correlations between prompt $\\Lambda_{c}^{+}$ baryons and charged particles in proton-proton collisions at 13 TeV, revealing differences from D-meson correlations that suggest possible modifications in charm quark hadronisation.

Contribution

First measurement of charm-baryon correlations with charged particles in pp collisions at 13 TeV, indicating potential differences in charm quark hadronisation processes.

Findings

$\\Lambda_{c}^{+}$-baryon triggers show more associated low-momentum particles than D-meson triggers.

Monte Carlo models underpredict associated particle yields at low $p_{\rm T}$.

Differences in correlation peaks suggest possible modified charm quark fragmentation or hadronisation.

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