QGP formation time and the elliptic flow of direct photons

20 May 2014, 16:30
spectrum (darmstadtium)



Board: G-20
Poster Electromagnetic Probes Poster session


Mrs Fu-Ming LIU (CCNU, Wuhan)


In this talk we investigate the information carried by the large elliptic flow of direct photons, observed at RHIC and LHC, in the frame work of (3+1)-dimensional ideal hydrodynamical model constrained with hadronic data. It is found that the transverse momentum spectra of direct photons can be explained much more easily, while a good explanation of the observed elliptic flow of direct photons can only be reached if the two time scales, thermal and chemical equilibrium are chosen properly, ie, about $1/3$~fm/c and 2~fm/c, respectively. The realization of thermal and chemical equilibrium are hot questions in relativistic heavy ion physics. The elliptic flow of direct photon serves as a more strict clock to those questions than other observables. High order harmonics of direct photons from PbPb collisions at 2.76~TeV are also predicted based on event-by-event fluctuation in this work, which look very similar to those of hadrons.
On behalf of collaboration: None

Primary author

Mrs Fu-Ming LIU (CCNU, Wuhan)

Presentation Materials