Distributions of the charged particles in the electromagnetic showers initiated by 5-1000 GeV electrons in Fe, W and Pb

Abstract

Distributions of the charged particles multiplicities in the electromagnetic showers initiated by 10 to 1000 GeV electrons in lead are calculated using GEANT4. It is shown that they are well fitted by the inverse sum of two exponents. The evolution of the multiplicity distribution shapes as a function of the lead depth is discussed. An estimate of the energy resolution of a simple e,γ detector consisting of a high Z convertor and a counter of the shower electrons and positrons is presented. IntroductionDetectors consisting of a lead converter and a position sensitive detector behind it are widely used in HEP experiments for e,γ/hadron and γ/π 0 separations and for e, γ coordinate and energy measurements [1][2][3][4][5][6][7][8][9][10][11][12][13]. They are often called preshower or shower maximum detectors. Their characteristics depend on the fluctuations of the charge particle flux in electromagnetic (EM) showers initiated in the converter by the primary e,γ. In our previous studies [14] it is shown that multiplicity distributions at the converter depth of t max , corresponding to the maximum of the charged particles flux in the EM showers, are asymmetric and have long tails at the low multiplicities due to late developments of some showers. They are well described by the inverse sum of two exponents: