Muon showers deep underground

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Abstract
Data gathered with the University of Utah neutrino detector during late spring and summer of 1967 were used to study penetrating muon showers. These downward-going events contained two or more nearly parallel muons incident in a range of zenith angles between 30 degrees and 75 having penetrated from 1500 to 6000 hg cm-2 of rock overburden. Studies were made to determine the radial extent of the showers, the frequency of occurrences of showers of each multiplicity, and the degree of isotropy of the arrival directions of shower events was plotted in celestial coordinates, with the result that these shower events could be characterized by a radius of 6 to 10 m, a multiplicity spectrum which is a power law in multiplicity having an exponent between -3.4 and -4.0 and no observable anisotropy. These shower data, together with measurements of events containing a single penetrating muon, were used to derive an empirical shower density function that accounts for the energy and angular dependence of the events of multiplicity 1, 2 and 3, as well as the absolute numbers of these events observed.