Quantum vs. semiclassical description of in-QGP quarkonia in the quantum Brownian regime

Abstract

In this work, we explore the range of validity of the semiclassical approximation of a quantum master equation designed to describe the $c\bar{c}$ dynamics in a quark gluon plasma at various temperatures, in the quantum Brownian regime. We perform a comparative study of various properties, e.g. the charmonia yield, of the Wigner density obtained with the Lindblad equation and with the associated semiclassical Fokker-Planck equation. The semiclassical description is found to reproduce with a remarkable accuracy the results obtained through the full quantum description. We show that, to a large extent, this can be attributed to the non-unitary components of the dynamics that result from the contact of the $c\bar{c}$ subsystem with the thermal bath, leading to a rapid classicalization of the subsystem.