Heavy-Light Susceptibilities in a Strongly Coupled Quark-Gluon Plasma

TL;DR

This paper extends a partonic T-matrix approach to finite chemical potential to calculate heavy-light quark susceptibilities in a strongly coupled quark-gluon plasma, aligning well with lattice QCD data and suggesting the presence of bound states in the medium.

Contribution

It introduces a generalized T-matrix method at finite chemical potential to compute susceptibilities, incorporating new parameters fitted to lattice data, and predicts bound states in the QGP.

Findings

Qualitative agreement with lattice QCD for heavy-light susceptibilities.

Indication of broad D-meson and charm-light diquark bound states in the QGP.

Transport properties consistent with a strongly coupled system.

Abstract

Quark number susceptibilities as computed in lattice QCD are commonly believed to provide insights into the microscopic structure of QCD matter, in particular its degrees of freedom. We generalize a previously constructed partonic $T$-matrix approach to finite chemical potential to calculate various susceptibilities, in particular for configurations containing a heavy charm quark. At vanishing chemical potential and moderate temperatures, this approach predicts large collisional widths of partons generated by dynamically formed hadronic resonance states which lead to transport parameters characteristic for a strongly coupled system. The quark chemical potential dependence is implemented into the propagators and the in-medium color potential, where two newly introduced parameters for the thermal and screening masses are fixed through a fit to the baryon number susceptibility, $\chi^B_2$. With this setup, we calculate heavy-light susceptibilities without further tuning; the results qualitatively agree with the lattice-QCD (lQCD) data for both $\chi^{uc}_{11}$ and $\chi^{uc}_{22}$. This implies that the lQCD results are compatible with a significant content of broad $D$-meson and charm-light diquark bound states in a moderately hot QGP.