Researches on the Magnetic Deflection of the Hard Component of Cosmic Rays

The energy spectrum and positive excess of the hard component of cosmic rays have been investigated both in Rome (50 m above sea level) and at Pian Ros\`a (350 m above sea level) by means of a counter system with deflecting magnetized cores. The results of several measurements are discussed, and the following interpretation is suggested: (1) A positive excess of the order of 20 percent is found in the hard component, in agreement with the results of other investigators. (2) The hypothesis of the existence of several types of mesons is not confirmed in the lower atmosphere (between 0 and 5000 m). (3) Assuming for the ratio τμc² between the meson proper lifetime τ and the rest energy μc² the value τμc²=3×10^-8 sec./Mev, one has to assume that the energy spectrum of mesons at the top of the atmosphere does not follow a power law E^-2.9 for low values of the energy (E<4×10⁹ ev).