A Program to Determine Fundamental Nuclear Data from Muon Intensity Measurements and to Investigate Geophysical Aspects of Cosmic Rays at High Energies: Initial Results

A collaborative investigation of high-energy cosmic ray muons is described in terms of experiments in progress, the theoretical calculations which provided the motivation for the experimental work, and the ultimate goals of the research. An instrument which is being constructed for the measurement of spark chamber tracks is described and recent results from the Mont Blanc experiment are presented. One has determined from these results that the slope of the depth-intensity curve of underground muons is steeper at muon energies around 1000 BeV than is indicated by surveys of the published literature. From this experimental observation it is concluded that either muon dE/dx processes increase more rapidly with energy than is usually assumed, or the muon energy spectrum at ground level steepens around 1000 BeV. This latter possibility could be the result of an energy-dependent change in the slope of the primary cosmic ray spectrum, meson production processes, or the fundamental properties of the mesons. The X-process (direct muon production), which predicts a flatter spectrum, does not provide an explanation of the Mont Blanc observation. (Author)