Nonperturbative Heavy-Flavor Transport Approach for Hot QCD Matter

Abstract

The heavy charm and bottom quarks are unique probes of the transport properties of the quark-gluon plasma (QGP) and its hadronization in high-energy nuclear collisions. A key challenge in this context is to embed the interactions of the heavy quarks in the expanding medium compatible with the strong-coupling nature of the QGP, and thus to unravel the underlying microscopic mechanisms. In the present work we progress toward this goal by combining recent $T$-matrix interactions for elastic scattering with an effective transport implementation of gluon radiation, and apply these in a Langevin framework in a viscous hydrodynamic evolution. Hadronization of heavy quarks is evaluated using a modern recombination model with 4-momentum conservation, supplemented with fragmentation constrained by data in proton-proton collisions. Deploying this approach to charm-hadron observables in Pb-Pb collisions at the LHC yields fair agreement with experiment while also identifying areas of further systematic improvement of the simulations and its current input.

Figures (4)

• Figure 1: Charm-quark friction (left panel) and spatial-diffusion coefficient (right panel) from selfconsistent heavy-light $T$-matrices in a strongly coupled QGP for the VCP (red lines) and WLC (blue lines) scenarios, compared to lQCD data Altenkort:2023eavAltenkort:2023omsHotQCD:2025fbd.
• Figure 2: Production cross sections of prompt $D^0$ (red), $D_s^+$ (green) and $\Lambda_c^+$ (blue) hadrons in $pp$ collisions at $\sqrt{s_{\mathrm{NN}}}$=5.02 TeV, using FONLL $c$-quark spectra (dashed line) and HQET fragmentation with statistical weights from the SHM, compared to ALICE data ALICE:2019nxmALICE:2022exq.
• Figure 3: Nuclear modification factor, $R_{\rm AA}$ (lower panels), and elliptic flow, $v_2$ (upper panels), of $D^0$ mesons at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\text{ TeV}$, calculated from our integrated HF transport and hadronization approach using $T$-matrix interactions with VCP (red lines) or WLC (blue lines) constraints. The red band in the lower left panel illustrates a shadowing range of 70–80% (the default is 75%). Experimental $R_{\rm AA}$ and $v_2$ data are from Refs. ALICE:2021rxaCMS:2017qjw and ALICE:2020iugCMS:2020bnz, respectively. The dashed lines in the left panels are for $c$-quarks just prior to hadronization.
• Figure 4: $D_s^+/D^0$ ratio in Pb-Pb(5.02 TeV) collisions at a hadronization temperature of $T_H$=160 MeV. The bands reflect a range of the strange-quark mass of $m_s$=0.4-0.45 GeV. ALICE data are taken from ALICE:2021kfcALICE:2019nxm