Nuclei as generators of quasi-real photons

Abstract
An equivalent photon approximation is tested for the inelastic scattering of high-energy non-hadronic particles (leptons and photons) in the electromagnetic field of nuclei. Coherent, incoherent elastic and incoherent inelastic contributions are included. As for the coherent (Coulomb) term, various nuclei (₉₂U²³⁵, ₂₇Co⁵⁹, ₆C¹²) with different types of form factors are considered. Four processes are considered : a) photoproduction of muon pairs ; b) muon bremsstrahlung ; c) muon trident producion (term with the time-like photon only) ; d) neutrinoproduction of a vector boson. The comparison of the approximation with the exact calculation is made for dσ/dW, where W is the invariant mass of the nonhadronic system produced. The approximation works well in general. As an application, we show the full calculation of the trident process (except for the correction due to the Pauli principle).