Low Energy Mesons in the Atmosphere

The dependence on altitude of the intensity of slow mesons, mesons with ranges less than 100 g ${\mathrm{cm}}^{-2\mathrm{}}$, has been measured by the method of delayed coincidences for atmospheric depths down to 250 g ${\mathrm{cm}}^{-2\mathrm{}}$. The intensity at this depth is thirty times that at sea level, and the variation with the depth $x$ is approximately as $\exp (-\frac{x}{\alpha })$ where $\alpha$ is 220 g ${\mathrm{cm}}^{-2\mathrm{}}$. The differential range spectrum of mesons at sea level has been measured by the same method for ranges between 10 g ${\mathrm{cm}}^{-2\mathrm{}}$ and 200 g ${\mathrm{cm}}^{-2\mathrm{}}$. The spectrum is nearly flat in this interval, the value at the lower limit being 0.9 of that at the upper limit. The data which are available in the literature have been examined to obtain the differential range spectrum of mesons whose ranges are greater than 100 g ${\mathrm{cm}}^{-2\mathrm{}}$ and less than 3×${10}^4$ g ${\mathrm{cm}}^{-2\mathrm{}}$, and to obtain the variation with altitude of the intensity of fast mesons—mesons with ranges greater than 100 g ${\mathrm{cm}}^{-2\mathrm{}}$.