Precision Measurement of Charge Symmetry Breaking innpElastic Scattering at 347 MeV

Charge symmetry breaking in $\mathrm{np}$ elastic scattering at 347 MeV has been measured with high precision. From fits of the measured asymmetry curves over the angular range $53.4°\le {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 86.9°$, the difference in the center-of-mass zero-crossing angles of the analyzing powers was determined to be $0.438°\pm 0.054°\left(\mathrm{stat}\right)\pm 0.051°\left(\mathrm{syst}\right)$. Using the experimentally determined slope of the analyzing power, $\mathrm{dA}/d\theta =(-1.35\mathrm{}\pm 0.05)\times {10}^{-2\mathrm{}}{\mathrm{deg}}^{-1\mathrm{}}$, this is equivalent to $\Delta A=[59\pm 7(\mathrm{stat})\pm 7(\mathrm{syst})\pm 2(\mathrm{syst}\left)\right]\times {10}^{-4\mathrm{}}$. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with this result.