Measurement of the π- absorption length in iron between 15 and 140 GeV/c

The interaction length of a particle can be measured directly by studying the attenuat ion of a particle beam in a material. The number of particles which have not interacted after a depth z of absorber is given by .N(z) = .N0 exp [-z/k], .N o being the incoming flux. In an unseparated negative high-energy beam, pions predominate, and the number of particles which have not suffered an interaction is given by