High transverse momentum of γ-ray bundles in air showers at 1014 eV regions

Results of analysis of high energy γ-ray bundles (ΣE sub(γ) >= 2 TeV) observed together with associated air showers at Mt. Norikura (738 gcm-2) are reported. The lateral distribution of γ-rays gives the average transverse momentum at least 2.3 sub(-0.7)sup(+0.8) GeV/c for the forward jet of secondaries, which is equal to 0.57 sub(-0.09)sup(+0.13) GeV/c for each neutral pions, with respect to the collision axis, at the energy region around 1014 eV. EAS size dependence of γ-ray bundles suggests high multiplicity and increasing transverse momentum. However, if the rapid change of primary composition is assumed, the interpretation without any drastic change of interaction may be possible. (author)