Strangelets, strangeness and antimatter: Results from the experiment NA52 at CERN

We present results of the CERN experiment NA52 which measures Pb+Pb collisions at 158 A GeV. The topics we address are: 1. strangelet search, 2. nuclei and antinuclei production and 3. strangeness production. No strangelets have been found. We set upper limits which stretch down to the minimal values of ~ 2 10^-10 for negatively and 3 10^-9 for positively charged strangelets. We observed 5³He near midrapidity. Nuclei and antinuclei cross sections suggest production mainly through coalescence, out of a thermalised particle source, at the time of the thermal freeze-out as witnessed by their temperature of 100-120 MeV. Charged kaons per participant nucleon (N_p) show an onset of enhancement followed by saturation at N_p ~ 80, corresponding approximately to an initial energy density of_i ~ 1.3 GeV/fm³. This onset may be connected to the onset of the QCD phase transition.