Application of an Improved Molière Theory to the Description of the Landau-Pomeranchuk-Migdal Effect

We present exact analytical and numerical results for high-energy Coulomb corrections (CCs) to the parameters of an improved Molière multiple scattering theory over a wide range of the nuclear charge number Z of the target atom and show that the values of these corrections increase up to 40% − 45% for Z = 92. We also report our results of applying this improved Molière multiple scattering theory for calculating CCs to the quantities of the classical Migdal theory of the Landau-Pomeranchuk-Migdal (LPM) effect, and we demonstrate that the improved Migdal LPM effect theory allow one to completely eliminate the discrepancy between the predictions of the LPM effect theory and their measurement at least for high-Z targets. We also obtained analytical and numerical results concerning high-energy CCs to the quantities of the quantum Migdal theory of the LPM effect in the ranges of Z from 6 to 92 and the Molière expansion parameter B from 4.5 to 8.5, and we managed to show that the magnitude of relative CC to the spectral radiation rate reaches −19% in these ranges considered and must be borne in mind, e.g., in the Monte-Carlo analysis of electromagnetic cascade LPM showers in extremely high-energy region.