The jet quenching parameter $\widehat{q}$ 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. $\widehat{q}$ 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 $\widehat{q}$ is increasing with increasing anisotropy. Possible implications for the saturation scale $Q_s$ in $A\text{−}A$ collisions are pointed out.

• Received 23 June 2008

DOI:https://doi.org/10.1103/PhysRevC.78.064906