Quark number scaling of $v_2$ in transverse kinetic energy and it's   implications for coalescence models
  We find that a simple extension of the coalescence model is sufficient to incorporate the perfect quark number scaling behavior of the elliptic flow in transverse kinetic energy, recently discovered by the PHENIX Collaboration. The flavor dependence of the elliptic flow can be consistently described in the low and intermediate $p_T$ if the transverse kinetic energy is conserved in the $2\to1$ or $3\to1$ parton coalescence process at the hadronization. Thus suggesting the quark coalescence as a possible hadronization mechanism at low $p_T$ as well. 
Jiangyong Jia and Chun Zhang