Medium modifications of kaons in pion matter

Abstract

Kaon in-medium masses and mean-field potentials are calculated in isotopically symmetric pion matter to one loop of chiral perturbation theory. The results are extended to RHIC temperatures using experimental data on $\ddot{I}€K$ scattering phase shifts. The kaon in-medium broadening results in an acceleration of the $\ddot{I}•\to K\bar{K}$ decay. The increased apparent dilepton branching of the $\ddot{I}•$-mesons, observed recently by NA50, NA49, and the PHENIX collaborations at RHIC, is interpreted in terms of rescattering of secondary kaons inside of the pion matter.

5 pages, 2 figures, revised version accepted for publication in PRL