The contribution of hard processes to elliptic flow
  I study a possible effect of momentum deposition from many hard partons traversing the hot and dense region produced early in nuclear collisions at the LHC. The expected number of such hard partons is large. It is argued that the induced diffusion wakes which carry the momentum deposited to the medium may interact. Due to azimuthally asymmetric geometry in non-central collisions, this may lead to small preference of the collective flow in the direction of the impact parameter. As a result, a small contribution to the azimuthal asymmetry of hadronic spectra is obtained. It may be important to take even such a small contribution into account if quantitative conclusions about early thermalisation and low viscosity are to be made, based on the measurements of the elliptic flow parameter v2. 
Boris Tomasik