From the following link we learn that the Klein-Nishina Formula for Photon-Electron Scattering gives the total cross section proportional to, 1/mass^2. http://demonstrations.wolfram.com/KleinNishinaFormulaForPhotonElectronScattering/ [Broken] Using this fact can I infer that when a short pulse of high energy photons (E > mass electron) interacts with a plasma, that there will be a temporary polarization of the plasma? How does the mass of particles scattered by a high energy neutrino effect the total cross section? Is there a similar 1/mass^2 factor in the total cross section? Thanks for any help!