Atmospheric Muon Flux at Sea Level, Underground, and Underwater

摘要

The vertical sea-level muon spectrum at energies above 1 GeV and theunderground/underwater muon intensities at depths up to 18 km w.e. arecalculated. The results are particularly collated with a great body of theground-level, underground, and underwater muon data. In the hadron-cascadecalculations, the growth with energy of inelastic cross sections and pion,kaon, and nucleon generation in pion-nucleus collisions are taken into account.For evaluating the prompt muon contribution to the muon flux, we apply twophenomenological approaches to the charm production problem: the recombinationquark-parton model and the quark-gluon string model. To solve the muontransport equation at large depths of homogeneous medium, a semi-analyticalmethod is used. The simple fitting formulas describing our numerical resultsare given. Our analysis shows that, at depths up to 6-7 km w. e., essentiallyall underground data on the muon intensity correlate with each other and withpredicted depth-intensity relation for conventional muons to within 10%.However, the high-energy sea-level data as well as the data at large depths arecontradictory and cannot be quantitatively decribed by a single nuclear-cascademodel.