Rupa Chatterjee

Elliptic flow of thermal photons in relativistic nuclear collisions.

We predict the transverse momentum (p(T)) dependence of elliptic flow of thermal photons for Au + Au collisions at the BNL Relativistic Heavy Ion Collider. We model the system hydrodynamically, with a thermalized quark-gluon plasma at early times followed by hadronization and decoupling. Photons are emitted throughout the expansion history. Contrary to hadron elliptic flow, which increases monotonically with p(T), the elliptic flow nu2(p(T)) of thermal photons is predicted to first rise and then fall again. Photon elliptic flow at high p(T) reflects the quark momentum anisotropy at early times when it is small, while at low p(T) it mirrors the large pion momentum anisotropy during the late hadronic emission stage. An interesting structure is predicted at intermediate p(T) approximately 0.4 GeV/c, where photon elliptic flow reflects the momenta and the (compared to pions) reduced nu2 of heavy vector mesons in the late hadronic phase.

Elliptic flow of thermal photons from an event-by-event hydrodynamic model

Elliptic flow of direct photons in relativistic heavy ion collisions is believed to be dominated by contribution from thermal radiation of quark gluon plasma up to

Elliptic flow of thermal photons and formation time of quark gluon plasma at energies available at the BNL Relativistic Heavy Ion Collider (RHIC)

p_T

Single photons from relativistic collisions of lead nuclei at energies available at the CERN Super Proton Synchrotron (SPS): A reanalysis

\sim 5

Formation Time of QGP from Thermal Photon Elliptic Flow

GeV/

Elliptic Flow of Thermal Photons/Dileptons☆

c

Production of Charm Quarks in a Parton Cascade Model for Relativistic Heavy Ion Collisions at

, although other sources start outshining the thermal contribution at already smaller values of

\sqrt{s_{\textrm NN}}

p_T

= 200 GeV

in the direct photon spectrum. The elliptic flow of thermal photons from ideal hydrodynamics considering a smooth initial density distribution under-predicts the PHENIX direct photon data from 200A GeV Au+Au collisions at RHIC by a large margin in the range