A Search for Irregularities in the Absorption of Cosmic Rays in Lead

Abstract

The integral absorption curve of cosmic rays has been examined at sea level up to a thickness of 365 cm of lead. In the first place, the absorption curve was examined in sections using a control telescope method to reduce the effects of atmospheric variation. It was found, to an accuracy of within about 1%, that there was no deviation from a monotonically decreasing curve. By a second method two regions of the curve, namely 0-30 cm and 71-193 cm, were examined in greater detail. Five Geiger-Muller counter telescopes were employed so that five consecutive points on the absorption curve were determined simultaneously. No irregularities in the absorption curves for these two regions were found, and it was also shown for the 0-30 cm region that this was true whether the absorber was wholly above or wholly within the telescope. The fact that no irregularities were found in the 71-193 cm region (corresponding to a momentum range of about 1-3 kMeV/C for μ-mesons) indicates that the irregularities in the meson momentum spectrum suggested by Blackett, and by Glaser, Hamermesh and Safonov are probably due to poor statistics.