Cosmic Ray Hard Showers below Ground

概要

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The hard showers observed with a large multiplate cloud chamber at 50 and 250 mwe underground were analysed. These showers have been classified according to the nature of their parents. Then, the relative frequency of π-to μ-induced shower γ, become to be γ_<50>=0.46±0.22 and γ_<250>=0.69±0.29. These results are considered to be in agreement with the conclusion of theoretical calculation. The energy of each μ-induced shower is obtained assuming the three models; (1) a model of collisions at a c.m.s. of the virtual photons and the nucleons, (2) one fire-ball model and (3) the model of constant transverse momentum of secondary particles. The energy distributions obtained are compared with those of Williams-Weizsacker method and following conclusions are obtained: (1) The value of photo-nuclear cross section is constant till several tens of BeV of showers energy.
1962-02-05