Abstract

We investigate the production mechanisms of p, d, t, He-3, He-4, Li-6, (p) over bar, (d) over bar and (He-3) over bar in Pb+Pb collisions at 158 A GeV measured near zero transverse momentum with the NA52 experiment at the CERN SPS. We find evidence that nuclei and antinuclei in Pb+Pb collisions are mainly produced via the coalescence mechanism out of a thermalized source of hadrons, at a time close to the thermal freeze-out of hadrons corresponding to a temperature of similar to120 MeV.