Does Feynman scaling remain valid at ultra-high energies?

Cosmic ray showers and particle physics at energies1015-1018eV

“…It is unlikely that the composition could be determined in more detail than this. After this work was completed we received a paper by Ouldridge and Hillas (1978) in which it is shown that an improved fit to the data on~"vs~, can be obtained with Feynman scaling (for both slope and magnitude) for an ordinary mixed composition and a galactic steepening at 2. 5x 10" eV per nucleon (see Footnote 7) provided the cross section continues to increase with energy as shown in tbe (log E)' extrapolation of Fig.…”

Particle Collisions Above 10 TeV as Seen by Cosmic Rays

“…In the indirect approach, the energy dependence of the assumed cross section is only one of several fe atures of the input model of hadronic interactions to which the calculated properties of air showers are sensitive. The general conclusion is, however, that ifhadronic scaling remains valid to '" 1 017 e V then the cross section must continue to increase at least as fast as shown in Figure 12 in order to prevent calculated showers from penetrating further into the atmosphere than is observed (Ouldridge & Hillas 1978). This conclusion also depends on the primary composition, as discussed in Section 7 above, but since a considerable fraction of heavy nuclei is also required the conclusion stands.…”

“…Ouldridge & Hillas (1978, Hillas 1979a) used a mixed composition (intermediate between the low energy composition and that described in Table 2) and an interaction model based on radial scaling of accelerator data. They find agreement with many features of air showers, such as the J1./e ratio, which had previously been difficult to reconcile with hadronic scaling.…”