φ meson propagation and decay at finite temperature

We study spectral properties of the φ meson at finite temperature using an effective Lagrangian together with finite-temperature field theory as a basis for modeling. General field-theoretic arguments are then used to establish the lifetime of φ in hot hadronic matter. We find from the model, and we therefore propose a scenario in which, the phi decays inside the fireball. Early decays into μ+μ- occur at high temperature while measurable hadronic decays into K+K- (not suffering rescattering) occur at freezeout, where flow could be substantial. These results provide a consistent picture, if not possible interpretation of NA49 and NA50 data from CERN. (author)