New Limits on the Difference Between the Muon- and Electron-Nuclear Interactions

Muonic-atom and electron-nucleus scattering measurements of nuclear radii have been examined in light nuclei in order to test their relative consistency. The electron data were selected to provide information at the "equivalent momentum transfer," which is approximately 0.3 ${\mathrm{fm}}^{-1\mathrm{}}$. All corrections known to us were applied or considered. Scattering experiments normalized to the Darmstadt ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ cross-section work are found to exhibit a systematic difference from the muon results. When these experiments are renormalized to the recent Amsterdam ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ work, the discrepancy disappears. In the latter case, no muon/electron measurements disagree by more than 0.02 fm. We estimate the standard deviation to be 0.014 fm about a mean of -0.002 fm. The possibility of anomalous lepton-nucleon interactions is discussed. The limits found here still admit observable anomalous effects in, for example, muonic H and He Lamb shifts and muon-nucleon scattering experiments.