Complex heavy-quarkonium potential in an anisotropic collisional quark-gluon plasma

Abstract

We compute the complex heavy-quark potential in an anisotropic quark-gluon plasma (QGP) using kinetic theory with a Bhatnagar-Gross-Krook collision kernel. By incorporating momentum anisotropy and a finite collision rate into the medium dielectric response, we derive both the real and the imaginary parts of the in-medium potential. The real part of the inverse dielectric function is obtained from the retarded/advanced gluon propagator, while the imaginary part is determined from the Feynman (symmetric) propagator. We find that collisions have only a minimal impact on the real part of the potential, suggesting a similarly weak effect on the binding energy. In an anisotropic plasma, the Weibel instability induces a pinch singularity that can render the imaginary part of the potential ill-defined; we show that sufficiently large collision rates regularize this singularity, yielding a well-defined imaginary potential in the corresponding region of parameter space. In this well-defined regime, collisions significantly enhance the magnitude of the imaginary part and modify the effect of anisotropy. This enhancement leads to larger quarkonium thermal widths and dissociation rates in a nonequilibrium QGP, providing further insight into quarkonium suppression mechanisms.