Cosmic Bays, at Large Zenith iVngles.

Abstract

The sea-level momentum spectrum and positive-negative ratio of cosmic ray muons incident at large zenith angles have been measured with a spectrograph comprising Geiger counters, neon flash-tubes and a solid iron magnet. Precise differential momentum spectra have been derived in the momentum range 3 – 550 GeV/c over the zenith angular range 77.5 - 90 . In the lower momentum region, 5-44 GeV/c, there is good agreement with the spectrum determined with the earlier Geiger counter spectrograph. Refined methods of measurement of the flash tube data for particles with momentum greater than 50 GeV/c lead to a maximum detectable momentum of the instrument, based on the probable error of deflection measurements, of (369 ± 16) GeV/c. The positive-negative ratio of muons at production has been found to be consistent with the results of similar experiments in the vertical direction in that the charge ratio does not tend to unity at least before several hundred GeV/c, indicating that the fluctuation in the multiplicity of high energy collisions increases with increasing energy. A determination is made of the expected ratio of the production spectra of muons from K-mesons and pions and this is compared with the measured ratios. No evidence is found for K-mesons playing an important role in the production of muons of energies above 100 GeV. At low energies, the statistical accuracy of the measurements is too low to permit a conclusion to be drawn about the importance of K-meson production; it is found that the muon spectra at low energies are comparatively insensitive to the nature of the parent particles and very high statistical accuracy would be required in order to make an estimate of K-meson production. The measurements have been combined with other data and used to estimate the ratio of production of charged K-mesons to pions in proton-air nucleus collisions and it is found that the upper limit of this ratio falls from O.65 at a proton energy of 10(^3) GeV to 0.2 at 2.10(^4) GeV. It is concluded that there is no evidence for a rapid increase in the K/πratio over a range of primary proton energies extending from a few GeV to some 500,000 Ge(^V) , and that the ratio is probably less than 0.4 over all energy ranges.