QGP formation time and the large photon v2 puzzle in heavy ion collisions

We investigate the large photon ν₂ puzzle and the two time scales (thermal and chemical equilibrium) in heavy ion collisions. The two-time-scale picture has a weak effect on the transverse momentum spectrum of direct photons, but a strong effect on the elliptic flow of direct photons. Thus both the spectrum and the elliptic flow of direct photons may be explained with hydro evolution constrained with hadron data. In such a picture, a gluon dominant matter appears in heavy ion collisions. This new matter may impact strongly to other fields such as astrophysics and cosmology.