In this paper the high-energy expansion for scattering from extended targets that the authors previously applied to beamstrahlung radiation and pair production is applied to the problem of radiation in a medium with multiple scattering. The suppression of the emission of long-wavelength photons, the Landau-Pomeranchuk-Migdal effect, is treated and explained in physical terms. This treatment of single-photon emission extends previous classical treatments of the problem to the quantum domain and corrects certain approximations made in these earlier works. The effects of finite target thickness is treated. A quantum treatment of multiple scattering is also given to aid in the physical interpretation of the suppression effect and to completely define our model of multiple scattering.

• Received 2 October 1995

DOI:https://doi.org/10.1103/PhysRevD.53.6265