The spectrum and charge-ratio of high energy cosmic rays

Abstract

The momentum spectrum and positive-negative ratio of cosmic ray mesons in the near vertical direction at sea- level, have been measured. The statistical accuracy and maximum detectable momentum are higher than have previously been attained by other workers using similar methods. This has been made possible by the modification of a Geiger counter spectrograph and addition of flash-tube arrays. Past particles have been selected electronically, and their trajectories recorded automatically by cameras which photograph the flash-tubes. A precise differential u-meson momentum spectrum has been derived in the momentum range 5 - 1000 GeV/c, after the usual instrumental corrections. In the lower momentum region, 5 - 10 GeV/c, there is good agreement with the spectrum determined with the Geiger counters alone. The measurements in the range 10 - 100 GeV/c are consistent with a T-meson production spectrum of constant exponent, γ = 2.64 ± 0.05. More accurate methods of measurement of the flash-tube data at higher momenta lead to a maximum detectable momentum of the instrument, based on the probable error of deflection measurements, of 657 ± 112 GeV/c. In the momentum range 70 to 700 GeV/c these independent measurements lead to a value of Y = 2,67 ± 0.10 and it must be concluded that there is little change in the exponent of the ₸-meson production spectrum in the whole range of measurement. The positive-negative ratio of μ-mesons at sea- level has been found to increase from about 1.25 at 250 GeV/c to about 1.5 at 250 GeV/c where the results are the first measurement made at such high momenta. The measurements have been used to study the energy loss processes of γ-mesons and also to study the production of ₸-mesons in the primary interactions.