Coherent scattering of high-energy photons in a medium - art. no. 116008

The coherent scattering of a photon in a Coulomb field (Delbruck scattering ) is considered for the momentum transfer Delta<<m in the frame of the quas iclassical operator method. In the high-energy region this process occurs o ver a rather long distance. The process amplitude is calculated taking into account the multiple scattering of particles of the intermediate electron- positron pair in a medium. The result is the suppression of the process. Li miting cases of weak and strong effects of the multiple scattering are anal yzed. The approach used is the generalization of the method developed by th e authors for the consideration of the Landau-Pomeranchuk-Migdal effect.