Renormalization of spectral lineshape and dispersion below Tc in   Bi2Sr2CaCu2O8+d
  Angle-resolved photoemission (ARPES) data in the superconducting state of Bi2Sr2CaCu2O8+d show a kink in the dispersion along the zone diagonal, which is related via a Kramers-Kronig analysis to a drop in the low-energy scattering rate. As one moves towards (pi,0), this kink evolves into a spectral dip. The occurrence of these anomalies in the dispersion and lineshape throughout the zone indicate the presence of a new energy scale in the superconducting state. 
A. Kaminski, M. Randeria, J. C. Campuzano, M. R. Norman, H. Fretwell,   J. Mesot, T. Sato, T. Takahashi, K. Kadowaki