Electromagnetic Probes I
- Charles Gale (McGill University (CA))
173. Thermal photons from a modern hydrodynamical model of heavy ion collisions: status of the direct photon puzzle
Jean-Francois Paquet (McGill University)
9/30/15, 9:00 AM
Early fluid-dynamical calculations of direct photon spectra and momentum anisotropy were found to be systematically smaller than measurements from the RHIC and the LHC, an observation that became known as the "direct photon puzzle". It is shown in this work that the use of a modern hydrodynamical model of heavy ion collisions  together with more complete photon emission rates greatly...
Koichi Hattori (RIKEN-BNL Research Center)
9/30/15, 9:20 AM
Electromagnetic probes have been expected to be penetrating probes of the early-time dynamics and quark-gluon plasma. Indeed, the photon spectra measured in the recent RHIC and LHC experiments provide us with an opportunity to deepen understanding of the photon emission mechanism, as they have significantly larger anisotropies compared to theoretical estimates by the hydrodynamic modeling of...
Dr Richard Petti (Brookhaven National Lab)
9/30/15, 9:40 AM
Photons are unmodified once produced in heavy ion collisions, so they provide information about the entire thermal evolution of the medium. PHENIX measured photon yields exceeding that expected from initial hard scattering and observed a large azimuthal anisotropy, $v_2$, of these soft photons with respect to the reaction plane. The large yield and $v_2$ continue to challenge...
Baldo Sahlmuller (Johann-Wolfgang-Goethe Univ. (DE))
9/30/15, 10:00 AM
Direct photons produced in the hot fireball of a heavy-ion collision leave the medium unscathed. Therefore, they are believed to provide information about the very early stage of the collisions. In particular, the direct photon pT spectrum at low pT (1 < pT < 4 GeV/c) might contain information about the initial temperature of the quark-gluon plasma and its space-time evolution. With current...