The spectrum of cosmic rays underground and at sea-level

From a measurement of the momentum spectrum of cosmic rays at different depths in the atmosphere and underground, information can be obtained on the interaction properties of the primary radiation and on the energy loss relation at high energies. Measurements of the spectra at 37.7 m.w.e. below sea-level and at sea-level have been made with magnetic spectro graphs employing the new technique of neon flash-tubes to locate the trajectories at the detecting levels. From a comparison of the spectrum at sea-level with that at 37.7 m.w.e. information has been gained on the energy loss of μ-mesons in the range 3-12 GeV. A study of the energy loss up to 158 GeV has also been made from a comparison of the sea-level spectrum with the depth-intensity curve. The conclusion of these experiments is that up to 158 GeV the energy loss of μ-mesons is in accord with that expected theoretically.