Andrzej S. Krys

High-energy photoproduction in air showers

A number of observations of Cygnus X-3 have been made and evidence has been reported for emission of PeV and TeV gamma rays from this object. The results given by the experimental data include the surprising fact that the number of muons involved in the showers induced by photons is not as small as expected. One way of explaining the observed excess of cosmic-ray muons in the gamma -ray induced showers is to postulate the rapid growth of the photonuclear cross section at energies 104 GeV. The authors examine in some detail the development of proton and gamma showers with full account for the photoproduction cross section. Both the lower and upper limits for the number of muons in gamma -initiated showers with photoproduction are calculated. It is shown that for gamma -initiated showers the number of muons is comparable with that in p showers if the rapid increase of the photoproduction cross section is assumed.

Photoproduction in gamma initiated showers

Our results show that the rapid growth of photonuclear cross section is connected with the excess of muons in gamma ray induced showers. We would like to point out that some γ‐initiated showers are similar to proton ones. If the spectra of gamma rays from point sources are flat, we may observe the excess in the primary flux near the knee. (AIP)

High energy gamma-families with halo and mass composition of primary cosmic rays in energy region above 10 PeV

Abstract The experimental spectrum of halo areas for gamma-families with Σ E γ ≥ 500 TeV is obtained and compared with simulations in quark-gluon string model. The comparison suggests a ∼ 2 times decrease of the proton fraction in primary cosmic ray (PCR) composition in the energy region 10 16 ÷ 10 17 eV. However at an energy above 10 17 eV, the experimental flux of halo events with area exceeding 300 ÷ 400 mm 2 is 5 ÷ 10 times larger than the simulated one. Such a difference may be explained by the assumption that in this region the fraction of protons increases as much as 3 times, while the slope of the spectrum decreases (γ = 2.6 ÷ 2.7).