Measurement of the Local Production of Muons Underground

The rate of stopping muons at a depth of 1.45 × ${10}^5$ ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$ has been measured with a view to checking the anomalously high rate observed by Baschiera et al. at Mont Blanc. Muons produced locally could be separately identified with a large spark counter array. Their rate agrees with expectation based on muoproduction of hadronic cascades in the rock. The Mont Blanc result cannot be reconciled with ours if the excess stopping muons are produced by high energy muons.