Particle out-scattering versus quasiparticle spectral width
= Particle out-scattering versus quasiparticle spectral width
A particle loss rate can include the factor $1-f(\xi)$, whereas a spectral decay width also contains the complementary inverse collision process. Their sum has the regular quadratic low-energy scale $\xi^2+(\pi k_BT)^2$. Particle and hole decay must not be confused with an occupied-state loss probability.