Low-Energy Differential Range Spectrum of Cosmic-RayμMesons

The differential range spectrum of cosmic-ray $\mu$ mesons was investigated in the region from 0 to 410 g/${\mathrm{cm}}^2$ Pb for evidence of minima. Delayed coincidences in a tank of liquid scintillator were used to identify stopping mesons. The spectrum decreases monotonically with decreasing energy and shows no irregularity. Although only relative readings were taken, the method is adaptable to a precision determination of the absolute range spectrum. The delay data yield for the natural mixture of sea level cosmic-ray $\mu$ mesons a mean life in carbon of 2.13±0.07 μsec.