Recent experimental data on Au+Au collisions from the Relativistic Heavy Ion Collider (RHIC) show a surprisingly large elliptic flow v2 that saturates at high transverse momenta pT > 2-3 GeV. A variety of theoretical approaches fail to reproduce this behavior.
Hadronization via parton coalescence provides a solution to the elliptic flow puzzle. Coalescence predicts a direct relation between v2 of a given hadron and the flows of its constituents, allowing one to extract v2 of partons. Furthermore, the flows of various hadron species are expected to be interrelated, which can be tested against available final and preliminary RHIC data.
Applying the coalescence formalism to charm hadrons, it is possible to extract charm quark v2(pT) from that of charm hadrons. This way experiments could determine to what degree charm quarks rescatter in the expanding parton medium and put important constraints on parton energy loss models.