Nonequilibrium evolution of quarkonium in medium

Yukinao Akamatsu,Takahiro Miura,A Rothkopf,L Tolos,D Röhrich,J.O Andersen,K Tywoniuk,A Tranberg,N Brambilla,A Kurkela

doi:10.1051/epjconf/202225801006

Abstract

We review recent progress in open quantum system approach to the description of quarkonium in the quark-gluon plasma. A particular emphasis is put on the Lindblad equations for quarkonium and its numerical simulations.

Highlights

Relativistic heavy-ion collision experiment provides us with a unique opportunity to study the novel matter composed of quarks and gluons, which are permanently confined inside hadrons at the energy scales of our daily experiences
Single heavy quark can probe the same property of the Quark-Gluon Plasma (QGP), but there is a big difference: a quarkonium is made of heavy quark-antiquark pair interacting with each other through attractive force if they are in the color singlet
There have been a lot of developments in understanding the non-equilibrium evolution of quarkonium in the QGP as an open quantum system [2,3,4], which we summarize in this article

Summary

Introduction

Relativistic heavy-ion collision experiment provides us with a unique opportunity to study the novel matter composed of quarks and gluons, which are permanently confined inside hadrons at the energy scales of our daily experiences. This attractive force binds the heavy quark pair so that its color is hidden inside the localized wave function In this sense, a quarkonium is a sensitive probe of QGP at higher temperatures, typically determined by its bound state size. Even though the complexity of heavy-ion collisions is enormous, the first step to describe a quarkonium as an open system is to derive a master equation in the simplest setup, namely the environment is a static and homogeneous QGP and the heavy quarks are the non-relativistic quantum mechanical particles. This simplification implicitly assumes that the (pseudo)critical temperature Tc is much lower than the heavy quark mass M so that one can find a temperature Tc < T ≪ M. With the overall picture given as above, we will review two essential ingredients in the open system descriptions for quarkonium — the master equation (Sec. 2) and its numerical simulation (Sec. 3)

Basics of open quantum systems

Simulation of the Lindblad equations for quarkonium

Density matrix

Equilibration and the effect of dissipation

Outlook