Towards the determination of heavy-quark transport coefficients in quark-gluon plasma

TL;DR

This paper systematically compares heavy-quark transport coefficients across various models in quark-gluon plasma, reducing uncertainties and highlighting the importance of realistic hydrodynamics and hadronization in interpreting heavy-flavor data.

Contribution

It provides a unified scheme to compare transport coefficients, significantly reducing the systematic uncertainties and emphasizing the role of realistic medium evolution and hadronization processes.

Findings

Systematic comparison reduces drag coefficient uncertainty to a factor of 2.

Realistic hydrodynamic evolution constrains heavy-quark transport coefficients.

Additional constraints can further decrease theoretical uncertainties.

Abstract

Several transport models have been employed in recent years to analyze heavy-flavor meson spectra in high-energy heavy-ion collisions. Heavy-quark transport coefficients extracted from these models with their default parameters vary, however, by up to a factor of 5 at high momenta. To investigate the origin of this large theoretical uncertainty, a systematic comparison of heavy-quark transport coefficients is carried out between various transport models. Within a common scheme devised for the nuclear modification factor of charm quarks in a brick medium of a quark-gluon plasma, the systematic uncertainty of the extracted drag coefficient among these models is shown to be reduced to a factor of 2, which can be viewed as the smallest intrinsic systematical error band achievable at present time. This indicates the importance of a realistic hydrodynamic evolution constrained by bulk hadron spectra and of heavy-quark hadronization for understanding the final heavy-flavor hadron spectra and extracting heavy-quark drag coefficient. The transverse transport coefficient is less constrained due to the influence of the underlying mechanism for heavy-quark medium interaction. Additional constraints on transport models such as energy loss fluctuation and transverse-momentum broadening can further reduce theoretical uncertainties in the extracted transport coefficients.