Z-scaling, high-pT direct photon and pi0-meson production at RHIC and LHC

Abstract

The scaling properties of direct photon production in pp, barpp and pA collisions at high energies is reviewed. The experimental data on the cross sections obtained at ISR, SpS and Tevatron are used in the analysis. The properties of data z-presentation, the energy and angular independencies, the power law, and A-dependence are discussed. The use of z-scaling to search for new physics phenomena in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions is suggested. The violation of z-scaling characterized by the change of the fractal dimension is considered as a new and complimentary signature of a nuclear phase transition. The cross sections of direct photon, pi0- and eta0-meson production in pp and pPb collisions at RHIC and LHC energies are predicted.