Momentum anisotropies in the quark coalescence model
  Based on the quark coalescence model, we derive relations among the momentum anisotropies of mesons and baryons in relativistic heavy ion collisions from a given, but arbitrary azimuthal distribution for the partons. Besides the familiar even Fourier coefficients such as the elliptic flow, we also pay attention to odd Fourier coefficients such as the directed flow, which has been observed at finite rapidity even at RHIC energies. 
Peter F. Kolb, Lie-Wen Chen, Vincenzo Greco, and Che Ming Ko