High pT azimuthal correlations: Elliptic flow

Initial anisotropy in coord. space (overlap) in non-central collisions translates into final azimuthal asymmetry in momemtum space (transverse to react. plane)
Exp. correlation functions:  v2 saturation at high pT:
Strong elliptic flow signal   strong (collective) pressure gradients
 large and fast (t<1.0 fm/c) parton rescattering (early thermalization).

Initial anisotropy in coord. space (overlap) in non-central collisions translates into final azimuthal asymmetry in momemtum space (transverse to react. plane)