Photons and pions from an expanding quark gluon plasma

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Abstract
Thermal emission of photons and surface leakage of hadrons from an expanding quark gluon plasma (QGP) likely to be formed in ultra-relativistic nuclear collisions are evaluated. A consistent formalism is developed to calculate the emission from the mixed phase. This lends a unique shape to the emission rates by introducing a change in their slopes as a function of the transverse momentum beyond 2 GeV for higher initial temperatures. It is argued that the transverse momentum window beyond 2 GeV is best suited for the detection of contributions from the QGP phase of the plasma. It is suggested that the measurement of these rates, along with the corresponding ( gamma / pi 0) ratios, may prove to be an efficient and unique signature of the quark gluon plasma. Results for SPS (super proton synchrotron), RHIC (relativistic heavy ion collider) and LHC (large hadron collider) energies are discussed.