THE PRODUCTION OF ANTI-MATTER IN OUR GALAXY

The discovery of a single anti-helium nucleus in the cosmic ray flux w ould definitely point toward the existence of stars and even of entire galaxies made of anti-matter. The presence of anti-nuclei in cosmic r ays has actually profound implications on the fundamental question of the baryon asymmetry of the universe. It is therefore crucial to deter mine the amount of anti-matter which our own galaxy already produces t hrough the spallation of high-energy protons on the interstellar gas o f the galactic disk. We have used here a coalescence model to assess t he amount of anti-deuterium and anti-helium (3) (H) over bar e present in cosmic rays together with anti-protons, The propagation of cosmic rays in the galaxy is described through a two-zone diffusion model whi ch correctly describes the observed abundances. We find that the (D) o ver bar/p ratio exceeds 10(-9) above a momentum per anti-nucleon of si milar to 4 GeV/c. Would the universe be purely made of matter, the AMS collaboration should be able to detect a few anti-deuterons during th e space station stage of the experiment. However, the 3 (H) over bar e /p abundance does not exceed similar to 4 X 10(-13) Heavier anti-nucle i are even further suppressed. (C) 1997 Published by Elsevier Science B.V.