High-energy pion interactions

Abstract

In this paper the results of a line scan of 640 cm of narrow-angle secondary tracks (E_Pt > 100 GeV) from proton primary jets in emulsions are presented. The proton component was eliminated by disregarding the smallest-angle track unless there was clear evidence that it did not represent a proton. The energy of each pion interaction found was estimated by the following procedure. The various energy estimators were modified to take account of multiple-collision events and then the energy and inelasticity which gave the closest agreement between the energy estimators E(charged), E(median), E(Castagnoli), E(quartile), and E_pt were used.The π-meson mean free path was found to be 40 cm (~26 mb) at an average energy of 450 GeV. The average multiplicity of the sample (of pion interactions) was found and shown to be consistent with a log E dependence. The average value of N_h was found and contrasted with previous results at lower energies. The results also show that on the average one pion carries away ~40% of the incident energy.In tracing the above path-length seven examples of direct pair production were identified giving a mean free path of 90 cm.