Momentum Spectra of Cosmic-Ray Mesons and Protons at Sea Level and 3.4-km Altitude

A cloud-chamber experiment has been performed at sea level and 3.4-km altitude to collect data on the momentum and scattering distributions of 15,000 mesons and protons. The momentum spectra and derived conclusions are discussed here. The meson momentum distribution at sea level is in accord with the results of others. A comparison of the sea-level and altitude spectra indicates that, for momenta between 0.7 and 3 $\frac{\mathrm{Bev}}{c}$, 0 to 15 percent of the mesons observed at sea level are produced below 3.4 km. Assuming that production of the fast mesons observed takes place within the top 125 g/${\mathrm{cm}}^2$ of the atmosphere, the differential momentum distribution of mesons at production can be represented adequately as an inverse power law with an exponent equal to 2.75±0.07, in good agreement with previous published results. The relative numbers of positive and negative particles at sea level agree well with those of other workers. At altitude the +/- ratio becomes quite large for the lower momenta (up to 2.5 as against 1.2 at sea level), while it approaches the sea-level ratio (1.3) for high momenta. Assuming that the difference between the sea-level and altitude ratios is due to protons, one can compute that above 0.3 $\frac{\mathrm{Bev}}{c}$ protons form 19±2 percent of all ionizing particles (excluding electrons) at 3.4 km. From the observed +/- ratios the proton momentum spectrum has been calculated.