Direct Pair Production by Muons

A measurement has been made of the direct pair production cross section for muon primaries between about 8 and 120 Bev. The muons were selected by a magnetic spectrometer and interactions were observed in a multiplate expansion cloud chamber. Results indicate that in the transferred-energy range above about 200 Mev the direct pair cross section is somewhat less than that predicted by the Murota-Ueda-Tanaka theory. This result does not, however, necessarily indicate any breakdown of fundamental electromagnetic theory. Possible theoretical inadequacies are discussed in the text.