Glueballs and statistical mechanics of the gluon plasma

Describing the gluon plasma as an ideal gas of transverse gluons with a temperature-dependent mass m(T) allows to reproduce its equation of state, computed in pure glue lattice QCD. Dealing with m(T) demands to build a thermodynamically consistent framework. We propose a general way to obtain such a formalism and apply it to the gluon plasma. Then we argue that the peculiar behavior of m(T) near the critical temperature Tc is due to color interactions between the gluons. Using an effective glueball model with a lattice QCD-derived screened color interaction, we show that those interactions are strong enough to bind the lightest glueballs up to 1.13 Tc. Moreover, the thermodynamical properties of the gluon plasma can be understood by describing it as a mixture of an ideal gas of free gluons and glueballs, with a temperature-dependent glueball abundance.