Study of cosmic ray composition in the knee region using multiple muon events in the Soudan 2 detector

Deep underground muon events recorded by the Soudan 2 detector, located at a depth of 2100 m of water equivalent, have been used to infer the nuclear composition of cosmic rays in the ``knee`` region of the cosmic ray energy spectrum. The observed muon multiplicity distribution favors a composition model with a substantial proton content in the energy region 8{times}10{sup 5}{endash}1.3{times}10{sup 7} GeV/nucleus. {copyright} {ital 1997} {ital The American Physical Society}