A simple expression for the entropy of a fireball from experimental strange particle ratios

Abstract

We derive an expression for the specific entropyS/N B in a non-interacting, non-relativistic Boltzmann gas mixture in terms of strange particle ratios like\(N_{\bar \Lambda } /N_\Lambda ,N_{\bar K} /N_K \),N K /N Λ andN Λ /N N . Then we investigate the influence of relativistic and quantum statistical effects and the role of hadronic interactions on reconstructing the specific entropy from the particle ratios. Since neglection of the relativistic effects causes the largest corrections, we include them in an improved expression. The resulting formula gives the specific entropy from the observed particle ratios with less than 20% error.