A Reanalysis of Single Photon Data at CERN SPS

Gale, Charles
Chatterjee, Rupa
Srivastava, Dinesh K.
Jeon, Sangyong
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We reanalyze the WA98 single photon data at CERN SPS by incorporating several recent developments in the study of prompt and thermal photon production from relativistic heavy ion collisions. Isospin and shadowing corrected NLO pQCD, along with an optimized scale for factorization, fragmentation and renormalization are considered for prompt photon production. Photons from thermal medium are estimated by considering a boost invariant azimuthally anisotropic hydrodynamic expansion of the plasma along with a well tested equation of state and initial conditions. A quantitative explanation of the data is obtained by combining $\kappa \times$ prompt with thermal photons, where $\kappa$ is an overall scaling factor. We show that, elliptic flow of thermal photons can play a crucial role to distinguish between the `with' and `without' phase transition scenarios at SPS energy.
Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, v2: minor corrections
Nuclear Theory