Landau-Pomeranchuk-Migdal effect for finite targets

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. copyright 1996 The American Physical Society