ARPES kink is a "smoking gun" for the theory of high-Tc superconductors:   dominance of the electron-phonon interaction with forward scattering peak
  The ARPES spectra in high-Tc superconductors show four distinctive features in the quasiparticle self-energy. All of them can be explained consistently by the theory in which the electron phonon interaction (EPI) with the forward scattering peak dominates over the Coulomb scattering. In particular, this theory explains why there is no shift of the nodal kink at 70 meV in the superconducting state, contrary to the clear shift of the anti-nodal singularity at 40 meV. The theory predicts a ``knee''-like structure of the imaginary part of the self-energy, which is phonon dominated for $\omega \approx \omega^{(70)}_{ph}$, and shows linear behavior for $\omega > \omega^{(70)}_{ph}$ - due to the Coulomb scattering. Recent ARPES spectra give that the EPI coupling constant is much larger than the Coulomb one. The dip-hump structure in the spectral function comes out naturally from the proposed theory. 
M. L. Kulic and O. V. Dolgov