On the characteristics of individual cascade showers with the LPM effect at extremely high energies

Characteristics of individual electromagnetic cascade showers in lead have been studied taking into consideration the Landau-Pomeranchuk-Migdal effect (LPM effect) through Monte Carlo simulation techniques. A total of 20 LPM showers have been simulated assumed to be initiated by photons or electrons of energy 10 17 eV. Each of the twenty simulated showers shows multi-peak structure during its longitudinal development unlike the smooth cascade curve obtained for showers simulated using Bethe-Heitler cross sections. It is shown that thin detectors with a depth of only few tens of radiation lengths, though good for observing showers without the LPM effect, do not provide reliable information on the real development of the LPM shower in extremely high energy regions.