Scattering of 2-Bev/cMuons in Carbon and Lead

The scattering cross section of high-energy μ mesons in carbon and lead has been measured, using a pure, monoenergetic beam of muons obtained with the Bevatron at the Lawrence Radiation Laboratory. Preparation, purification, and measured properties of the beam are described. The median momentum was 2.00±{}0.03 Bev/c, the spread in momentum was not more than ±{}3.5%, and the effective contamination due to pions was 4.9×{}10^-6. During the experiment the total number of muons incident on the apparatus was 2.5×{}10⁷. Counter hodoscopes recorded the muons scattered from 14.4 g/cm² of lead and from 27 g/cm² of carbon. Inelastic as well as elastic processes were accepted. Scattered particles were observed at angles up to 12^∘{} (momentum transfer {~}400 Mev/c). The lead data cover the same range as those cosmic-ray experiments which have appeared to indicate an anomalously large scattering. No anomaly is found; the lead scattering agrees closely with the distribution calculated by Cooper and Rainwater for purely electromagnetic interactions. The carbon data permit a better comparison with theoretical expectations, since one is measuring the single-scattering cross section directly, and one can account for the effects of nuclear structure rather accurately, using electron-scattering data and a detailed theoretical analysis of Drell and Schwartz. The carbon scattering results, based on 300 events in the region 70 Mev/c-400 Mev/c momentum transfer, agree closely with the Drell-Schwartz theory. The upper limits which this result places on a nonelectromagnetic scattering cross section and on a muon form factor are discussed.