On Theory of Landau-Pomeranchuk-Migdal Effect

Abstract

The cross section of bremsstrahlung from high-energy electron suppressed due to the multiple scattering of an emitting electron in a dense media (the LPM effect) is discussed. Development of the LPM effect theory is outlined. For the target of finite thickness one has to include boundary photon radiation as well as the interference effects. The importance of multiphoton effects is emphasized. Comparison of theory with SLAC data is presented.

Comparison of analytical and Monte Carlo calculations of multi-photon effects in bremsstrahlung emission by high-energy electrons

“…The present status of both the various theoretical approaches and the experimental results do not allow to test whether the bremsstrahlung in the field of the atomic electrons is subject to a different suppression than the bremsstrahlung in the field of the atomic nucleus, for which Migdal originally formulated his theory. The Coulomb correction term f was not included in Migdal work, but has been studied by Baier and Katkov [26], within their approach, showing that it can be incorporated with a redefinition of the form factors, as done here. It is also very difficult to understand the fate of the 1 À x term in Eq.…”

“…Baier and Katkov have also studied the multi-photon emission taking into account the LPM effect described by their own theory [26]. The LPM cross section depends separately on the two variables k and E and does not satisfy the functional form of Eq.…”

Comparison with experimental data of different theoretical approaches to high-energy electron bremsstrahlung including quantum coherence effects

“…Baier and Katkov (BK in the following) also studied the LPM effect in a series of papers [41,[59][60][61], trying to improve on the original treatment by Migdal [7] and including several additional features like boundary radiation and multi-photon effects. In order to simplify the comparison with other theoretical approaches, we restrict the description of their work to the case of a semi-infinite target.…”

“…The potential V is then refined to take into account the Coulomb correction by defining a parameter θ 2 = θ 1 e f (Z α)−1/2 where f is the Bethe-Maximon Coulomb correction rederived, by a different method, in Appendix A of Ref. [59]. The authors then determine the effective impact parameter ρ c giving the main contribution to the cross section.…”

Variation of radiation length due to LPM effect

“…This important feature was absent in the previous calculations. The LPM effect in a thin target were the interference effects and boundary photon emission is of special interest was analyzed in [8]. The probability of multiphoton emission is enhanced at high energy [9].…”