Average transverse momentum and energy density in high-energy nucleus-nucleus collisions

Abstract

Emulsion chambers were used to measure the transverse momenta of photons or ${\ensuremath{\pi}}^{0}$ mesons produced in high-energy (\ensuremath{\ge}1 TeV/amu) cosmic-ray nucleus-nucleus collisions. A group of events having large average transverse momenta have been found which apparently exceed the expected limiting values. Analysis of the events at early interaction times, of the order of 1 fm/c, indicates that the observed transverse momentum increases with both rapidity density and energy density.