The Zenith Angle Dependence of Cosmic-Ray Protons

The proton spectrum for particles in the momentum band 0.4-1.0 Bev/c and the meson spectrum for particles in the momentum band 0.09-0.34 Bev/c at zenith angles 45° east, vertical, and 45° west have been obtained at 3.3-km elevation and magnetic latitude 48° north. The zenith angle dependence of protons, along with a simplified analysis, is presented as data on the nucleonic cascade. It is found taht the gross zenith angle dependence will fit a ${cos}^{3.2}\theta$ distribution at 45 degrees east and west, there being no statistically significant east-west asymmetry. The simplified calculation assumes that a unidirectional component of the primary radiation will (1) suffer exponential absorption along its original path with a path length for removal of 120 g/${\mathrm{cm}}^2$ of air and (2) acquire an ultimate distribution at 3.3 km due to scattering fitting a ${cos}^n\omega$ law, $n$ being an adjustable parameter.