High energy cosmic rays, particle physics and astrophysics

At energies of 1015 to 1018 eV particles degrade their energy more rapidly in traversing the atmosphere than do low‐energy particles– i.e. there is a departure from simple scaling– but if the rapid rise in hadronic cross‐sections continues so far one need assume no other change in the average characteristics of interactions seen at accelerators to explain a wide range of characteristics of air showers, though discordant sets of data still permit different interpretations. If one such discord, between shower size spectra obtained in the (old) Chacaltaya experiment and experiments at lower altitudes, were to be resolved in favour of the latter, one would obtain a cosmic‐ray energy spectrum fitting very well to the low‐energy data, and the primary composition might also fit smoothly. A small shift in the energy scale might have significant consequences for the 1020 eV cut‐off. The ’’knee’’ in the spectrum near 3×1015 eV remains, and appears not to be an effect of magnetic trapping, but more probably a source...