Kinetic theory of a longitudinally expanding system of scalar particles

Thomas Epelbaum (1) , François Gelis (2) , Sangyong Jeon (1) , Guy Moore (3) , Bin Wu (2)

1 McGill University = Université McGill [Montréal, Canada]
2 IPHT - Institut de Physique Théorique - UMR CNRS 3681
3 Institut für Kernphysik [Darmstadt]

A simple kinematical argument suggests that the classical approximation may be inadequate to describe the evolution of a system with an anisotropic particle distribution. In order to verify this quantitatively, we study the Boltzmann equation for a longitudinally expanding system of scalar particles interacting with a $\phi^4$ coupling, that mimics the kinematics of a heavy ion collision at very high energy. We consider only elastic $2\to 2$ scatterings, and we allow the formation of a Bose-Einstein condensate in overpopulated situations by solving the coupled equations for the particle distribution and the particle density in the zero mode. For generic CGC-like initial conditions with a large occupation number and a moderate coupling, the solutions of the full Boltzmann equation do not follow a classical attractor behavior.

Domains: High Energy Physics - Phenomenology [hep-ph]; Nuclear Theory [nucl-th]

Thomas Epelbaum, François Gelis, Sangyong Jeon, Guy Moore, Bin Wu. Kinetic theory of a longitudinally expanding system of scalar particles. Journal of High Energy Physics, 2015, ⟨10.1007/JHEP09(2015)117⟩. ⟨cea-01280458⟩