Lifetime of the η′ meson at low temperature

Abstract

This work constitutes one part of an investigation of the low-temperature changes of the properties of the η meson. In turn these properties are strongly tied to the U (1) A anomaly of Quantum Chromodynamics. The final aim is to explore the interplay of the chiral anomaly and in-medium effects. We determine the lifetime of an η meson being at rest in a strongly interacting medium as a function of the temperature. To have a formally welldefined low-energy limit we use in a first step Chiral Perturbation Theory for a large number of colors. We determine the pertinent scattering amplitudes in leading and next-to-leading order. In a second step we include resonances that appear in the same mass range as the η meson. The resonances are introduced such that the low-energy limit remains unchanged and that they saturate the corresponding low-energy constants. This requirement fixes all coupling constants. We find that the width of the η meson is significantly increased from about 200 keV in vacuum to about 10 MeV at a temperature of 120 MeV.