The analyzing power ${\mathit{A}}_{\mathit{y}}$ for proton elastic scattering on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been precisely and absolutely determined at three scattering angles (${\mathrm{\theta }}_{\mathrm{lab}}$=16.3°, 17.3°, and 18.3°) at an incident proton energy of 188.9 MeV. The technique employed requires statistically high quality polarization transfer measurements, combined with the constraints imposed on polarization observables for reactions with the spin structure 1/2+0→1/2+0. These results represent some of the most accurately known spin observables at intermediate energies and serve as calibration points for secondary standards.

• Received 17 October 1991

DOI:https://doi.org/10.1103/PhysRevC.45.R504