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Title: Off-equilibrium photon production during the chiral phase transition

In the early stage of ultrarelativistic heavy-ion collisions chiral symmetry is restored temporarily. During this so-called chiral phase transition, the quark masses change from their constituent to their bare values. This mass shift leads to the spontaneous non-perturbative creation of quark–antiquark pairs, which effectively contributes to the formation of the quark–gluon plasma. We investigate the photon production induced by this creation process. We provide an approach that eliminates possible unphysical contributions from the vacuum polarization and renders the resulting photon spectra integrable in the ultraviolet domain. The off-equilibrium photon numbers are of quadratic order in the perturbative coupling constants while a thermal production is only of quartic order. Quantitatively, we find, however, that for the most physical mass-shift scenarios and for photon momenta larger than 1 GeV the off-equilibrium processes contribute less photons than the thermal processes. -- Highlights: •We investigate first-order photon emission arising from the chiral mass shift. •We provide an ansatz eliminating possible unphysical vacuum contributions. •Our ansatz leads to photon spectra being integrable in the ultraviolet domain.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1]
  1. Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt (Germany)
  2. (FIAS), Ruth-Moufang-Straße 1, D-60438 Frankfurt (Germany)
  3. Institutionen för fysik och astronomi, Uppsala Universitet, Box 516, 75120 Uppsala (Sweden)
Publication Date:
OSTI Identifier:
22220784
Resource Type:
Journal Article
Resource Relation:
Journal Name: Annals of Physics (New York); Journal Volume: 336; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CHIRAL SYMMETRY; COUPLING CONSTANTS; EQUILIBRIUM; HEAVY ION REACTIONS; INTEGRAL CALCULUS; PARTICLE PRODUCTION; PHOTONS; QUANTUM FIELD THEORY; QUARKS; RELATIVISTIC RANGE; SPECTRA; ULTRAVIOLET RADIATION; VACUUM POLARIZATION