Thermal Photons and Lepton Pairs from Quark Gluon Plasma and Hot Hadronic Matter

TL;DR

This paper investigates thermal photon and lepton pair production from quark-gluon plasma and hot hadronic matter using finite temperature field theory, highlighting observable differences at SPS, RHIC, and LHC energies.

Contribution

It presents a comprehensive formulation of photon and lepton pair production rates incorporating medium effects and compares signals from quark-gluon plasma and hadronic matter across different energy scales.

Findings

Thermal photon and dilepton spectra from QGP dominate at high transverse momentum.

In-medium effects significantly alter hadronic spectral functions at SPS energies.

QGP formation is likely at RHIC and LHC energies based on photon and dilepton signals.

Abstract

The formulation of the real and virtual photon production rate from strongly interacting matter is presented in the framework of finite temperature field theory. The changes in the hadronic spectral function induced by temperature are discussed within the ambit of the Walecka type model, gauged linear and non-linear sigma models, hidden local symmetry approach and QCD sum rule approach. Possibility of observing the direct thermal photon and lepton pair from quark gluon plasma has been contrasted with those from hot hadronic matter with and without medium effects for various mass variation scenarios. At SPS energies, in-medium effects of different magnitude on the hadronic properties for the Walecka model, Brown-Rho scaling and Nambu scaling scenarios are conspicuously visible through the low invariant mass distribution of dilepton and transverse momentum spectra of photon. However, at RHIC energies the thermal photon (dilepton) spectra originating from Quark Gluon Plasma overshines those from hadronic matter for large transverse momentum (invariant mass) irrespective of the models used for evaluating the finite temperature effects on the hadronic properties. It is thus expected that both at RHIC and LHC energies the formation of Quark Gluon Plasma in the initial stages may indeed turn out to be a realistic scenario.