Differential Range Spectrum of Cosmic-Ray Mesons at Sea Level

Operation of a cosmic-ray mass-measuring equipment under 8.8 inches of carbon absorber for 123 hours of sensitive time yielded 495 stopping mesons identifiable by their momentum vs residual range. After correction for zenith-angle and solid-angle dependence of the stopping particles, it is found that the spectrum of mu mesons for residual ranges 40-105 g/${\mathrm{cm}}^2$ air equivalent is flat and has an intensity of approximately 6.0×${10}^{-6\mathrm{}}$/g-sec-sterad.