Intervalley scattering by charged impurities in graphene
  Intervalley charged-impurity scattering processes are examined. It is found that the scattering probability is enhanced due to the Coulomb interaction with the impurity by the Sommerfield factor $F_Z\propto \epsilon^{2\sqrt{1-4g^2}-2}$, where $\epsilon$ is the electron energy and $g$ is the dimensionless constant of the Coulomb interaction. 
L.S. Braginsky and M.V. Entin
cond-mat.mes-hall