TY  - INPR
A1  - Dumitru, Adrian Bogdan
A1  - Bleicher, Marcus
A1  - Bass, Steffen A.
A1  - Spieles, Christian
A1  - Neise, Ludwig
A1  - Stöcker, Horst
A1  - Greiner, Walter
T1  - Direct photons in Pb+Pb at CERN-SPS from microscopic transport theory
N2  - Direct photon production in central Pb+Pb collisions at CERN-SPS energy is calculated within the relativistic microscopic transport model UrQMD, and within distinctly di erent versions of relativistic hydrodynamics. We find that in UrQMD the local momentum distributions of the secondaries are strongly elongated along the beam axis initially. Therefore, the preequilibrium contribution dominates the photon spectrum at transverse momenta above H 1.5 GeV. The hydrodynamics prediction of a strong correlation between the temperature and radial expansion velocities on the one hand and the slope of the transverse momentum distribution of direct photons on the other hand thus is not recovered in UrQMD. The rapidity distribution of direct photons in UrQMD reveals that the initial conditions for the longitudinal expansion of the photon source (the meson fluid ) resemble rather boostinvariance than Landau-like flow.
KW  - Quanten-Molekular-Dynamik
KW  - UrQMD
KW  - Kollisionen schwerer Ionen
KW  - SPS
KW  - heavy-ion collisions
KW  - UrQMD
KW  - Quanten-Molekular-Dynamic
KW  - SPS
Y1  - 2005
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3075
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30-23230
ER  -