BOSE-EINSTEIN CONDENSATION OF PIONS IN ULTRARELATIVISTIC NUCLEUS-NUCLEUS COLLISIONS AND THE SPECTRA OF KAONS

The properties of a pion gas that is formed in ultrarelativistic colli sions of nuclei are studied in the Weinberg model for pi pi interactio n. The possible Bose-Einstein condensation of a dense pi(-) gas is con sidered. The Green's function and the spectrum of the overcondensate e xcitations are calculated. For a weak condensate, the results coincide with those obtained in [1] in the lambda phi(4) model (lambda = const ), while for a developed condensate there are significant differences. The properties of kaons are considered for temperatures below the cri tical temperature for Bose-Einstein pion condensation. It is shown tha t, in the presence of a condensate, the K- effective mass becomes subs tantially larger, while the K+ effective mass becomes smaller. These f eatures may manifest themselves in the observable momentum distributio ns of kaons.