The analysis of 4.5 BeV negative pion interactions in nuclear emulsion

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Abstract
Two hundred nuclear interactions produced in Ilford G5 nuclear emulsion by 4.5 Bev π- mesons have been analysed. The transverse momentum of those secondary shower particles identified as pions has an average value over all angles of 290±50 MeV/C. The mean multiplicity of shower particles from the interactions is 2.0 ± 0.1 and is independent of the number of heavily ionizing prongs Nh . About 90 % of the shower particles were estimated to be pions. The angular distribution in the C-system is anisotropic with a mean value for |cos θ*verbar; of 048 ± 0.03. Assuming that secondary pions are emitted symmetrically backwards and forwards from a single collision system, the observed angular distribution of shower particles has been used to determine the effective mass of the collision partner. It is found to be 1.40+0.47 −0.27 proton mass units. If the total distribution is divided into groups with respect to Nh , it is found that events having Nh ≤7 yield a value of 0.77+0.36 −0.19 proton mass Units whilst those having Nh 7 yield 2.3+0.9 −0.4 proton maas units.