Asymmetry of the dielectron emission rate in an isospin-asymmetric pion medium

The dielectron emission by pion annihilation in an isospin-asymmetric pion gas at finite temperature is considered. Due to the difference between the longitudinal and transverse parts of the in-medium ϱ meson self-energy a specific asymmetry of the rates is caused for electron pairs with relative momenta perpendicular or parallel to the total pair momentum. This asymmetry may be considered as a sensitive signal of in-medium modifications of the ϱ properties.