A study of cosmic ray protons at ground level

Abstract

The momentum spectra of cosmic ray protons and pions up to an energy of I50 GeV have been measured at Durham, 198 feet above sea-level. Assuming a particular model for the interaction of high energy nucleons, a new estimate has been made of the primary cosmic ray nucleon spectrum. This may be represented in the energy range 10(^10) to 3 x 10(^13) eV nucleon by the expression:-I(>E) = 0.87(^+0.52) (_-0.30) E(^-1.58) cm(^-2) sec(^-1) Sterad(^-1) where E is in units of GeV. It has been shown that a model in which the mean value of the elasticity of nucleon=air nucleus collisions is not a function of ' incident energy describes the experimental results accurately. The value found for the fraction of this energy retained by the incident nucleon is 53%. The effect of large fluctuations in elasticity from collision to collision has been investigated and found to be negligible. The result of taking fluctuations into account is to give a mean value of elasticity ~3% lower than the value obtained assuming the elasticity not to fluctuate.