The photoproduction threshold. Implications for air showers

The high energy behavior of photoproduction is controlled by the hadronic structure function of the photon and it is possible that the cross section may increase rapidly after a threshold energy beyond which the gluon content of the photon is fully developed. One consequence would be an increase in the muon content of air showers generated by ≅ PeV photons. Although one can qualitatively change the muon content of photon showers by assuming a generous estimate of the magnitude of enhanced photoproduction, we still find that only a small fraction of photon showers look like normal hadronic showers, contrary to indications from some recent air shower experiments. (orig.)