Elasticμ−Scattering in Nuclear Emulsion

An emulsion stack was exposed to a separated beam of ∼2×${10}^7$ ${\mathrm{\mu }}^{-}$ of energy 52±8 MeV at the CERN synchrocyclotron. Muons with endings in a region near the incoming edge of the plates were traced back to scatters, thus discriminating in favor of events with momentum transfers from 100-160 MeV/c. The 78 events found give evidence that the muon behaves merely as a heavy electron, in contradiction to the anomalous muon-nucleus scattering reported in several cosmic-ray experiments. Our data indicate, however, a possibility of a small amount of scattering in excess of that predicted, particularly for momentum transfers >130 MeV/c. This may be ascribed either to unresolvable inelastic scattering, to inaccuracies in the parameters of the nuclear charge distribution, or to the breakdown in the representation of the many-body nucleus by a smoothed-out potential. Of the 78 events, one was an elastic scatter by hydrogen, which is consistent with the Mott scattering formula.