The momentum spectrum of μ mesons at 37 m water equivalent underground
J. E. Cousins;W. F. Nash;
A direct measurement of the momentum spectrum of μ-mesons with momenta greater than 1 GeV/c has been made under Castle Rock, Nottingham, at a depth of 37.24 m w.e. The spectrograph consisted basically of two 28 cm diameter cloud chambers; one above and one below the air gap of a large permanent magnet. The measured spectrum contains 1481 particles. The results have been analysed by comparing the experimental spectrum with spectra derived from the sea-level momentum spectrum measured by the Manchester group, assuming various values of the energy loss of the fast particles in the rock. The experiment shows that the most probable value of the energy loss in the rock is 7.5 GeV for μ-mesons arriving underground with momenta in the range 1 GeV/c to 20 GeV/c. These results are in satisfactory agreement with the authors’ calculations and illustrate the importance of the « density correction » in collision loss calculations.
