Experimental Tests of Cascade Theory at High Energies

Results of simultaneous measurement of the radial position and angular orientation of electrons in ten high-energy (180-2000-BeV) electromagnetic cascades are given. Six of these cascades were developed in pure emulsion, while four were developed in a lead-emulsion sandwich stack. Numerical calculations of the angular distributions, both within approximation B and the core approximation, are presented. Calculations on the mixed radial-angular distribution are related to the separate distributions. A method is given for the use of the mixed distribution to extend the effective radial range of measurement to such an extent that the transition of the experimental results from the core approximation to approximation B becomes evident. Limited experimental verification of the often-used approximation B is thereby established. It is further shown that cascade theory is internally consistent within the region of validity of the core approximation and that the radial range must extend up to ∼${10}^{-1\mathrm{}}$ radiation length in order to include all particles having angles as small as ∼4-5 deg.