Investigating charm quark interactions and hadronization in PbPb collisions with $\mathrm{D}_{s}^{\pm}$ and $\mathrmΛ_{c}^{\pm}$ measurements

TL;DR

This work investigates charm-quark interactions and hadronization in the QGP created in Pb-Pb collisions by measuring the elliptic and triangular flow, $v_2$ and $v_3$, of prompt $D_s^{±}$ and the nuclear modification factor $R_{AA}$ for $Λ_c^{±}$, as well as the $Λ_c^{±}/D^0$ yield ratio across collision systems. The CMS analysis combines high-statistics Pb-Pb data with hadronic-decay reconstruction and a TMVA-based selection to extract prompt signals and flow via a scalar-product method. The results show $D_s^{±}$ flow consistent with $D^0$, and a strong suppression of $Λ_c^{±}$ in Pb-Pb with an enhanced $Λ_c^{±}/D^0$ at low $p_T$, supporting charm hadronization via coalescence with strange quarks and space-momentum correlations; high-$p_T$ behavior approaches pp expectations, challenging purely fragmentation-based pictures. The measurements provide quantitative constraints on charm energy loss and hadronization in the QGP, testing coalescence and recombination scenarios and informing model development.

Abstract

Charm quarks serve as a sensitive probe of the Quark-Gluon Plasma (QGP), providing direct insights into its formation, evolution, and properties. In this proceeding, we present new high-precision measurements from the CMS experiment in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV. The elliptic ($v_2$) and triangular ($v_3$) flow of prompt $\mathrm{D}_{s}^{\pm}$ mesons are measured with high precision, extending the kinematic coverage. A comparison of the $\mathrm{D}_{s}^{\pm}$ flow to that of $\mathrm{{D}^{0}}$ mesons is performed to investigate the impact of strange quark hadronization on charm quark collectivity. We further explore charm quark hadronization by measuring the $\mathrmΛ_{c}^{\pm}$ nuclear modification factor ($R_{AA}$) as a function of transverse momentum for different collision centralities, and the $\mathrmΛ_{c}^{\pm}$/$\mathrm{{D}^{0}}$ yield ratio in pp, pPb, and Pb-Pb collisions. These results provide crucial constraints on charm quark energy loss and hadronization mechanisms, offering critical tests for theoretical models and advancing our understanding of heavy quark dynamics in the QGP.

Figures (2)

• Figure 1: (upper panel) The $v_2$ coefficients for prompt $\mathrm{D}_{s}^{\pm}$ and prompt $\mathrm{{D}^{0}}$ (from Ref. CMS-D0-2) mesons as a function of $\mathrm{p}_\mathrm{T}$ for the 0--10% (left), 10--30% (middle), and 30-50% (right) centrality classes. (lower panel)The $v_3$ coefficients for prompt $\mathrm{D}_{s}^{\pm}$ and prompt $\mathrm{{D}^{0}}$ mesons as a function of $\mathrm{p}_\mathrm{T}$ for the 10--30% centrality class. The vertical bars and the boxes represent statistical and systematic uncertainties, respectively. The figures are from the reference PAS-HIN-24-006.
• Figure 2: (left) The nuclear modification factor $R_{AA}$ versus $\mathrm{p}_\mathrm{T}$ for prompt $\mathrm{\Lambda}_{c}^{\pm}$ production in centrality regions of 0–90% (stars), 0–10% (squares), 10–30% (triangles), 30–50% (inverted triangles) and 50–90% (diamonds) in PbPb collisions. (right)The ratio of the production cross sections of prompt $\mathrm{\Lambda}_{c}^{\pm}$ to prompt $\mathrm{{D}^{0}}$ versus $\mathrm{p}_\mathrm{T}$ for 0–90% (closed stars) and 0–10% (closed squares) centrality classes of PbPb collisions are compared to the pp result. The vertical bars and the boxes represent statistical and systematic uncertainties, respectively. The figures are from the reference Lc.