Abstract
We describe the energy distribution of hard gluons travelling through a dense quark–gluon plasma whose temperature increases linearly with time, within a probabilistic perturbative approach. The results were applied to the thermalization problem in heavy ion collisions. In the weak coupling picture this thermalization occurs from “the bottom up”: high energy partons, formed early in the collision, radiate low energy gluons which then proceed to equilibrate among themselves, forming a thermal bath that brings the high energy sector to equilibrium. We see that, in this scenario, the dynamic we describe must set in around t sim 0.5 fm/c after the collision in order to reach a fully thermalized state at t sim 1 fm/c. We then look at the entropy density and average temperature of the soft thermal bath, as the system approaches (local) thermal equilibrium.
Highlights
We describe the energy distribution of hard gluons travelling through a dense quark–gluon plasma whose temperature increases linearly with time, within a probabilistic perturbative approach
Once it has reached a local thermal equilibrium, it is described by relativistic hydrodynamics
Is that assumption valid in the thermalization scheme? During the last bottom-up stage, the temperature of the soft thermal bath increases linearly with time, even during the system’s expansion, due to the hard gluons which serve as an energy source [2]
Summary
The quark–gluon plasma (QGP) formed in the collision is, initially, highly anisotropic and out of equilibrium. As it expands, the QGP undergoes several stages that are characterized by different degrees of freedom and described by different effective theories. The QGP undergoes several stages that are characterized by different degrees of freedom and described by different effective theories Once it has reached a local thermal equilibrium, it is described by relativistic hydrodynamics. The main shortcoming to our goal is that previous results, which focus on jet quenching, assume that the high-energy partons travelling through the medium do not alter T in a significant way.
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