2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48673We discuss a new kind of correlation, the correlation of particle-antiparticle pairs emitted back-to-back in the local rest frame of a medium, if medium effects cause mass modification of the quanta. The theory of these new correlations is summarized for relativistically expanding, locally thermalized sources.8 pages, LaTeX, sprocl.sty, epsfig.sty, 2 eps figures, Proc. Correlations and Fluctuations'98, Matrahaza, Hungary, June 14-21, 1998, (World Scientific, Singapore, 1999, ed. T.Csorgo, S. Hegyi, G. Jancso and R. C. Hwa) p. 547High Energy Physics - Phenomenologytext