Emission of heavy charged particles in relativistic nucleus--nucleus collisions. [500 MeV, nuclear energy and angular distributions, cross section, tables

Abstract

The energy and angular distributions of nuclei produced in interactions of 500 MeV/nucl /sup 40/Ar projectiles with an Au target were investigated. Nuclei with charge 3 < or = to Z < or = to 11 were observed. Single particle inclusive spectra were obtained at angles between 35 and 85/sup 0/, in the energy range 20 to 60 MeV/nucl. The spectra decrease monotonically with the increasing energy, angle, and charge. The distributions are consistent with an isotropically emitting source recoiling with an average velocity of aproximately 0.08 c in the beam direction. Thermal model fits to the data yield temperatures tau of about tau approximately 60 MeV. The low recoil velocity and high temperature are shown to be in conflict with energy and momentum conservation. Two nonthermal models of emission involving expansion or rotation are explored. Although neither of these models gives good quantitative fits to the data, they do much better than the thermal model if it is constrained to be energy and momentum conserving. The data for all energies, angles and species may be simply parameterized. When transformed into a recoiling source frame with ..beta../sub 0/ approximately equal to 0.08, all data points lie near (+-4x) a common curve, for which the invariant cross section, f identical with (1/p) (d/sup 2/ sigma/d..cap omega..dE), falls exponentially with increasing momentum, f varies as e/sup /sup -/p/p/sub c//, with a characteristic momentum p/sub c/ approximately equal to 340 MeV/c.