Test of charge symmetry in n‐p elastic scattering at 480 MeV

An experiment to investigate the isospin‐mixing charge‐symmetry breaking component in the n‐p interaction is under way at TRIUMF. The experiment measures the difference ΔA between the neutron and proton analyzing powers An and Ap in n‐p elastic scattering at 480 MeV. The experiment consists of two interleaved phases in which polarized (unpolarized) neutrons are scattered from an unpolarized (polarized) proton target of the frozen spin type. As a null measurement, requiring no accurately known polarization standards, the experiment determines the difference in angle at which An and Ap cross through zero. It intends to provide an unambiguous test of class IV charge‐symmetry breaking effects to the level of ΔA≂0.001, corresponding to a laboratory angle difference at zero crossing of ∼0.04°.