Heavy Quarkonium in Extreme Conditions

Abstract

In this report we review recent progress achieved in the understanding of heavy quarkonium under extreme conditions from a theory perspective. Its focus lies both on quarkonium properties in thermal equilibrium, as well as recent developments towards a genuine real-time description, valid also out-of-equilibrium. We will give an overview of the theory tools developed and deployed over the last decade, including effective field theories, lattice field theory simulations, modern methods for spectral reconstructions and the the open-quantum systems paradigm. The report will discuss in detail the concept of quarkonium melting, providing the reader with a contemporary perspective. In order to judge where future progress is needed we will also discuss recent results from experiments and phenomenological modeling of quarkonium in relativistic heavy-ion collisions.

New developments in lattice QCD on equilibrium physics and phase diagram

“…Quarkonia are considered as a thermometer of medium produced in heavy-ion collisions and the fate of quarkonia states in the medium as well as transport coefficients are among the main topics in LQCD studies in extreme conditions [4,42]. Many new theoretical results obtained since last years' QM conference is overviewed in Ref.…”

“…A first continuum extrapolated results of J/ψ and Υ correlation functions have been obtained in quenched lattice QCD very recently [46]. The continuum extrapolation makes the direct comparison with pQCD computations possible, and thus alternatively from using inversion methods [42,47,48], the spectral functions are investigated by fitting to the correlators using a pQCD motivated ansatz [49]. It was found that no J/ψ peak is needed in the fit ansatz to describe the lattice correlator data T ≥ 1.1T c , while a resonance peak is still needed for Υ up to 1.5 T c as shown in the middle plot of Fig.…”

Thermal modifications of quarkonia and heavy quark diffusion from a comparison of continuum-extrapolated lattice results to perturbative QCD

“…To gain information on heavy quarkonium properties such as thermal modifications of bound states or transport coefficients, studies of the hadronic spectral function in the hot medium are needed [1,2]. On the lattice we cannot measure the spectral function directly, but instead calculate Euclidean correlators.…”

“…Many methods for this ill-posed extraction problem have been proposed, for a recent review see [1]. In our approach, we compare continuum extrapolated correlators obtained from fine quenched lattices to a perturbative spectral function, constructed by combining vacuum asymptotics with pN-RQCD calculations.…”

D meson mass and heavy quark potential at finite temperature

“…Since Matsui and Satz proposed the suppression of quarkonium in relativistic heavy-ion collisions as a signature of the quark-gluon plasma formation due to color screening [1], this phenomenon has been investigated in numerous theoretical and experimental studies (see, for instance, the recent review in Ref. [2]). One of the most critical quantities affecting quarkonium suppression is the potential between a heavy quark and anti-quark.…”