As estimation of the primary proton spectrum between 1012 and 1014 eV

Based on measurements of the unaccompanied charged hadron flux from 1011 to 1014 eV at mountain altitudes, the primary proton flux is estimated using recently determined proton-proton total cross sections from new measurements of the real part of the forward scattering amplitude at ISR, and Glauber theory to calculate the proton-air inelastic cross section. The derived spectrum agrees well with extrapolation of the direct measurements below 2 x 1012 eV without change of slope. (author)