Quasiparticle lifetimes in the charged Bose gas and the cuprates

The scattering cross section of a Coulomb potential screened by a charged Bose gas (CBG) is calculated both above and below the Bose-Einstein condensation temperature, using the variable phase method. In contrast with the BCS superconductor, the screened scattering potential and quasiparticle lifetime are found to be very different in the superconducting and normal states. We apply the result to explain the appearence of a sharp peak in the ARPES spectra in some cuprates below the superconducting transition.