No abstract

EDITOR 557 results are shown in Fig. 3. A plot of av (cross section X neutron velocity) against E shows a marked rise with energy, indicating a large scattering cross section or a strong resonance level at higher energy. The curve becomes nearly horizontal if a constant value of 15 X 10~2 4 cm 2 /atom is attributed to scattering, thus making the absorption cross section at 0.025 ev about 92X10" 24 cm 2 /atom. In the present measurement, however, much significance cannot be attributed to the value of the scattering cross section evaluated in this manner. Earlier measurements 4,5 at a single energy gave the absorption cross section for kT neutrons at about 75 X 10~2 4 cm 2 /atom.

No abstract

Fast (Rn+Be)

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 Rosa (3500 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 T//JLC 2 between the meson proper lifetime r and the rest energy nc 2 the value r//*c 2 = 3X 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<4X 10 9 ev).