Hall effect in the cuprates: the role of forward scattering on   impurities
  We solve the Boltzmann equation for electrons moving in a two-dimensional plane of square symmetry in the presence of a transverse magnetic field. We assume that there are two sources of scattering: a large momentum-independent scattering on a collective mode of the electron system, and a smaller momentum-dependent forward scattering on impurities. We show that the effect of impurities on the longitudinal and Hall conductivities is of the same order of magnitude. 
R. Hlubina