Gluon splitting rates in an anisotropic plasma in the AMY formalism

Abstract

We introduce a novel numerical method to obtain the gluon splitting rates in an anisotropic QCD plasma in the AMY formalism, suitable for an anisotropic collision kernel. The method extends previous works by decomposing the additional angular information into Fourier modes, resulting in a significantly larger system of differential equations to solve numerically. It is then tested by calculating the rates for a simple anisotropic model for the collision kernel, which is compared to a thermal system. Remarkably, the obtained rates can be well-approximated by the rates calculated from an angular-averaged collision kernel, while still deviating significantly from equilibrium. An isotropic model for the collision kernel that is commonly used in QCD kinetic theory simulations, and which relies on the infrared temperature $T_*$ and an effective Debye mass, leads to rates that significantly deviate from the nonequilibrium rate, particularly at smaller parton energies.