Momentum Broadening of a Fast Parton in a Perturbative Quark-Gluon Plasma

Understand

The average transverse momentum transfer per unit path length to a fast parton scattering elastically in a perturbative quark-gluon plasma is related to the radiative energy loss of the parton.

• We first calculate the momentum transfer coefficient $\hat q$ in terms of a classical Langevin problem and then define it quantum-mechanically through scattering matrix element.
• After treating the well known case of a quark-gluon plasma in equilibrium we consider an off-equilibrium unstable plasma.
• As a specific example, we treat the two-stream plasma with unstable modes of longitudinal chromoelectric field.