A Reanalysis of Single Photon Data at CERN SPS

TL;DR

This paper reanalyzes CERN SPS single photon data by integrating advanced prompt and thermal photon production models, highlighting the importance of thermal photon elliptic flow in identifying phase transition scenarios.

Contribution

It introduces a comprehensive reanalysis combining NLO pQCD with hydrodynamic thermal photon models, emphasizing the role of elliptic flow in phase transition detection.

Findings

Quantitative match of data with combined prompt and thermal photons using a scaling factor.

Elliptic flow of thermal photons can differentiate phase transition scenarios.

Enhanced understanding of photon production mechanisms at SPS energies.

Abstract

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.