A microscopic derivation of the quantum mechanical formal scattering   cross section
  We prove that the empirical distribution of crossings of a "detector'' surface by scattered particles converges in appropriate limits to the scattering cross section computed by stationary scattering theory. Our result, which is based on Bohmian mechanics and the flux-across-surfaces theorem, is the first derivation of the cross section starting from first microscopic principles. 
D. D\"urr, S. Goldstein, T. Moser and N. Zangh\`{\i}