Muon intensities and angular distributions deep underground

Abstract

Recent measurements of the intensity of muons below 3000 m.w.e. (metres water equivalent) underground have been combined to give an estimate of the depth-intensity relation and the angular distribution for atmospheric muons down to a maximum depth of approximately 9000 m.w.e. It is found that the vertical intensity can be represented by the expression I(0, h) = 9.8 × 10^-7 exp(-h/λ)cm^-2sec^-1sterad^-1 where h is the depth in m.w.e. and λ = 810 ± 50 m.w.e. The corresponding angular distribution at vertical depth h is given by I(θ, h) = I(0, h) secθ exp{-(h/λ)(secθ - 1)} where θ is the zenith angle. The implication of the above angular distribution for the estimate of neutrino fluxes in deep underground cosmic-ray experiments is discussed.