Dresden 2013 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 40: Schwerionenkollisionen und QCD Phasen
HK 40.7: Vortrag
Dienstag, 5. März 2013, 18:30–18:45, HSZ-204
Thermal Photons at RHIC — •Hendrik van Hees1, Ralf Rapp2, and Charles Gale3 — 1Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany — 2Cyclotron Institute, Texas A&M University, College Station, Texas 77843-3366, USA — 3Department of Physics, McGill University, 3600 University Street, Montreal, Canada H3A 2T8
Recent measurements of direct photons in 200 AGeV Au-Au collisions
at RHIC by the PHENIX collaboration find an unexpectedly large
anisotropic flow, v2 of these photons. Here we present a model for
thermal-photon emission from the matter created in the heavy-ion
collision, taking into account both the partonic (QGP) and hadronic
phases of the fireball evolution. For the corresponding thermal-photon
rates we use an HTL resummed pQCD matrix element for the emission from
the QGP and a hadronic model in the confined phase. Convoluting these
rates over the history of the fireball evolution within a simple
elliptic blastwave model we find the photon yield to be dominated by
radiation from the hadronic phase for qT ≲ 2-3 GeV,
leading to a direct-photon v2 comparable with the lower edge of the
error bars of the measurement. Also an analysis of the photon-qT
slopes shows consistency of our model with the data due to the blue
shift of the hadronic photon spectrum from the radial flow of the
thermal source, which compensates the lower temperatures of the
hadronic phase.
Supported by the Helmholtz Association through the ExtreMe Matter
Institute (EMMI) and BMBF.
[1] H. van Hees, C. Gale, R. Rapp, Phys. Rev. C 84, 054906 (2011)