Charmed baryon-to-meson ratios inside jets as a discriminator of hadronization mechanisms: from color reconnection in p+p to coalescence in Pb+Pb

Abstract

Jets separate the products of hard scatterings from the underlying event and thus help to clarify the origin of the enhanced baryon-to-meson ratios observed from small to large collision systems. We investigate the charmed baryon-to-meson ratio $Λ_c^+/D^0$ within jets in p+p and Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$~TeV to discriminate between candidate hadronization mechanisms. In p+p collisions, simulated with PYTHIA8 using color reconnection (CR-BLC Mode 2) as a representative beyond-leading-color scenario, the in-jet ratio is enhanced at low-to-intermediate $p_T$ relative to the inclusive one---opposite to the light-flavor $Λ/K^0_S$ case---because the color-reconnection-induced excess of the ratio remains correlated with the jet and survives the jet requirement, while the fragmentation baseline shows no such enhancement. In Pb+Pb collisions, described by the SHELL model with a coalescence plus fragmentation hybrid hadronization, the in-jet ratio is instead suppressed moderately at intermediate $p_T$, because coalescence hadrons assembled from soft thermal partons carry no correlation with the jet direction and are preferentially discarded by the jet selection. The sign of the in-jet modification thus discriminates between the two mechanisms. Both mechanisms shift charmed hadrons toward small values of the parallel jet momentum fraction $z^{ch}_{||}$, with a stronger effect on $Λ_c^+$, so that the $z^{ch}_{||}$ spectrum probes non-fragmentation hadronization independently of parton energy loss. The radial profile of the in-jet ratio rises with the distance from the jet axis in both systems, with the lowest-$p_T$ interval displaced farthest for color reconnection and the intermediate-$p_T$ interval for coalescence. These results provide the baseline and predictions needed for future jet-tagged charmed-hadron measurements in both collision systems.