Test of Charge Symmetry in Neutron-Proton Elastic Scattering at 477 MeV

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 Aₙ and Aₚ at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference is ${{θ}}₀ₙ({A}ₙ){-}{{θ}}₀ₙ({A}ₚ)=+0.13^∘{} ±{}0.06^∘{} (±{}0.03^∘{})$, 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 ${A}ₙ{-}{A}ₚ=+0.0037 ±{}0.0017 (±{}0.0008)$.