Nonperturbative Heavy-Quark Diffusion in the Quark-Gluon Plasma

Abstract: We evaluate heavy-quark (HQ) transport properties in a Quark-Gluon Plasma (QGP) employing interaction potentials extracted from thermal lattice QCD. Within a Brueckner many-body scheme we calculate in-medium T-matrices for charm- and bottom-quark scattering off light quarks in the QGP. The interactions are dominated by attractive meson and diquark channels which support bound and resonance states up to temperatures of ~1.5 T_c. We apply pertinent drag and diffusion coefficients (supplemented by perturbative scattering off gluons) in Langevin simulations in an expanding fireball to compute HQ spectra and elliptic flow in \sqrt{s_{NN}}=200 GeV Au-Au collisions. We find good agreement with semileptonic electron-decay spectra which supports our nonperturbative computation of the HQ diffusion coefficient, suggestive for a strongly coupled QGP.

Overview of Heavy-Quark Diffusion in the Quark-Gluon Plasma

The study "Nonperturbative Heavy-Quark Diffusion in the Quark-Gluon Plasma" provides a detailed investigation into heavy-quark (HQ) transport properties within the Quark-Gluon Plasma (QGP) using a Brueckner many-body scheme. This approach employs interaction potentials derived from thermal lattice QCD calculations, facilitating an enriched understanding of HQ interactions in a strongly coupled QGP, particularly in contrast to traditional perturbative Quantum Chromodynamics (pQCD) methods.

Methodology and Results

The authors implemented a nonperturbative $T$-matrix formalism to calculate the elastic charm- and bottom-quark scattering off light quarks within the QGP. This approach prioritizes attractive meson and diquark channels that can form resonance states up to temperatures approximately 1.5 times the critical temperature ($T_c$). These resonance formations lead to a drag coefficient that surprisingly increases with decreasing temperature, contrary to the predictions of perturbative QCD.

Key numerical results were derived using relativistic Langevin simulations, which enabled the computation of HQ spectra and elliptic flow during $\sqrt{s_{NN}} = 200$ GeV Au-Au collisions. The simulations showed a strong alignment with electron decay data, thereby supporting the nonperturbative characterization of HQ diffusion as indicative of a strongly coupled QGP.

Implications and Future Directions

The findings suggest significant implications for theory and experiment. The temperature-dependent dynamic seen in HQ transport coefficients challenges conventional assumptions based on pQCD regarding HQ relaxation times, illustrating a marked decrease with increasing temperature due to the dissolution of resonance states. This insight refines our understanding of thermalization processes in the plasma and suggests avenues for further experimental validation, specifically through direct lattice QCD computations of heavy-light quark correlation functions within the QGP.

Future studies should focus on enhancing precision regarding potential extraction methods from lattice QCD, as current variations contribute substantial uncertainties to the model predictions. Moreover, integrating radiative components of HQ energy loss at high momentum could complement the elastic scattering models, thus providing a comprehensive view of HQ interaction dynamics in high-energy collisions.

This advanced investigation heightens our appreciation of the nonperturbative interactions governing HQ dynamics within the QGP, presenting valuable insights that may inspire subsequent experimental and theoretical advancements in the broader field of high-energy nuclear physics.