Electromagnetic measurement of the temperature of quark-gluon plasma produced in central ultrarelativistic nuclear collisions

TL;DR

This paper estimates the maximum temperature of quark-gluon plasma produced in ultrarelativistic nuclear collisions by analyzing direct photon spectra, accounting for hydrodynamic expansion and equation of state effects.

Contribution

It introduces a method to determine the plasma temperature from electromagnetic measurements, considering non-exponential spectral corrections.

Findings

Photon spectrum exhibits near-exponential behavior

Maximum plasma temperature can be estimated from photon data

Non-exponential corrections are quantified

Abstract

Ultrarelativistic collisions of large nuclei produce a short-lived plasma of deconfined quarks and gluons. Of all the GeV-energy photons detected in these nuclear collisions, only a small number are emitted directly by the quark-gluon plasma. We use the characteristic near-exponential energy spectrum of these photons to estimate the maximum temperature of the plasma, assuming it undergoes hydrodynamic expansion. We quantify non-exponential corrections to the photon spectrum resulting from the characteristic equation of state and photon emission rate of nuclear matter.