Jet quenching and broadening: The transport coefficient q ̂ in an anisotropic plasma

The jet quenching parameter q is analyzed for a quark jet propagating in an anisotropic plasma. The momentum anisotropy is calculated at high temperature of the underlying quark-gluon plasma. q is explicitly estimated in leading-logarithmic approximation by the broadening of the massless quark interacting via gluon exchange. A plasma instability is present. Strong indications are found that q is increasing with increasing anisotropy. Possible implications for the saturation scale Q{sub s} in A-A collisions are pointed out.