Speaker
Jean-Francois Paquet
(McGill University)
Description
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 [1] together with more complete photon emission rates greatly improves agreement with both ALICE and PHENIX data, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy in heavy ion collisions. The event-by-event hydrodynamical model used includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. Different photon emission rates are investigated, including one that takes into account the effect of confinement on photon emission [2]. The effect of both shear and bulk viscosities on the photon rates is studied and is shown to have a measurable effect on the photon momentum anisotropy. The inclusion of parton energy loss on prompt photons and its importance for comparisons of direct photon calculations with experiments is discussed.
[1] Ryu, Paquet, Shen, Denicol, Schenke, Jeon and Gale. (2015) [arXiv:1502.01675]
[2] Gale, Hidaka, Jeon, Lin, Paquet, Pisarski, Satow, Skokov and Vujanovic. (2015) Phys. Rev. Lett. 114, 072301
| On behalf of collaboration: | NONE |
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Author
Jean-Francois Paquet
(McGill University)
Co-authors
Bjoern Schenke
(Brookhaven National Lab)
Prof.
Charles Gale
(McGill University)
Dr
Chun Shen
(McGill University)
Gabriel Denicol
(McGill University)
Matthew Luzum
(Universidade de Santiago de Compostela)
Sangyong Jeon
(McGill University)
