*10^<12>∿10^<15>eV 領域での一次宇宙線の"準"直接観測

概要

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We exposed emulsion chambers at the level of 32.8gr/cm^2 for∿30hrs, and∿800 showers were detected on X-ray films (Fuji #200-type), among which∿200 primaries (ΣE_γ≨2TeV, θ<75°) were identified by tracing back each recorded in successive plates of nuclear emulsion. On the basis of these primaries, we obtained I_p(≨E_0)=1.02・10^<-5>×(E_0/TeV)^<-1.82±0.10> No./cm^2・sec・str in the region 5≲E_0≲*100TeV for proton primary, and I_a(≨E_0)=6.50・10^<-7>×(E_0/TeV・nucleon)^<-1.75±0.10> No./cm^2・sec・str in the region 3≲E_0≲*10 TeV/nucleon for alpha primary. The former is clearly deviated from both data by Grigorov et al. and Zatsepin et al., and rather consistent with JACEE data. The latter is again in disagreement with Grigorov data, but nearly compatible with those obtained by JACEE and Zatsepin et al.. The γ-ray flux we observed covers the energy region 2∿80TeV, which is nearly consistent with the extrapolation from that obtained by Nishimura et al. in the region as low as 0.2∿2 TeV. We found, however, that it is much more abundant in our energy region than those coming from the proton-and alpha-primaries alone, indicating that heavy primaries, such as iron component, become effective in the primary energy 10^<14>∿10^<15>eV/nucleus.