2025/08/01 by Sambataro, Maria Lucia, Minissale, Vincenzo, Plumari, Salvatore +1 · 2 citations
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Nuclear Theory (nucl-th)
paper · doi:10.48550/arxiv.2508.01024
A central goal in the study of heavy-flavour production is to determine the interaction strength between Heavy Quarks (HQs) and the Quark-Gluon Plasma (QGP), quantified by the spatial diffusion coefficient Ds(T). Recent lattice QCD (lQCD) results with dynamical fermions suggest a remarkably low value of 2πT Ds ≈ 1 at T=Tc for charm quarks - significantly lower than both quenched QCD estimates and most phenomenological models - which typically yield 2πT Ds ≈ 3.5 - 5. This discrepancy raises the question of whether such a small Ds(T), corresponding to a thermalization time τth ≈ 1 - 1.5 fm/c, is compatible with experimental measurements of key observables like the nuclear modification factor RAA, the elliptic and triangular flow coefficients v2 and v3 for D mesons. Using an event-by-event Langevin transport framework, we analyze several scenarios and highlight the pivotal role played by the momentum dependence of the drag coefficient A(p) = τth-1(p). Our findings show that a small 2πT Ds (p→ 0)≈ 1 - 2 values can align with experimental data only if a significant momentum dependence in τth(p)=1/A(p) is included, as predicted by T-matrix approaches, or by the extended Quasi-Particle Model (QPMp). In contrast, assuming a momentum-independent τth = Mc DslQCD / T, it fails to reproduce the observed phenomenology. Furthermore, a short thermalization time of τth ≈ 1.5 fm/c implies a loss of sensitivity of the final-state observables to the initial charm-quark momentum distribution up pT ≈ Mc, suggesting a possible universal behavior driven by a dynamical attractor.