An experiment resulting in the first measurement of the isospin-mixing, charge-symmetry-violating component of the $n-p$ interaction has been performed. The experiment determined the difference in the angles of the zero crossing of the neutron and proton analyzing powers $A_n$ and $A_p$ at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference is ${\theta }_{0n}\left(A_n\right)-{\theta }_{0n}\left(A_p\right)=+0.13\mathrm{}° \pm 0.06° (\pm 0.03°)$, where the second error is a worst-case estimate of systematic error. The resulting difference in the analyzing powers at the zero-crossing angle is $A_n-A_p=+0.0037\mathrm{} \pm 0.0017 (\pm 0.0008)$.

• Received 31 March 1986

DOI:https://doi.org/10.1103/PhysRevLett.56.2571