Absolute measurement of thep+panalyzing power at 183 MeV

The analyzing power ${\mathit{A}}_{\mathit{y}}$ for p+p elastic scattering at ${\mathrm{\theta }}_{\mathrm{lab}}$=8.64°±0.07° (${\mathrm{\theta }}_{\mathrm{cms}}$=18.1°) and at a bombarding energy of 183.1±0.4 MeV has been determined to be ${\mathit{A}}_{\mathit{y}}$=0.2122±0.0017. The error includes statistics, systematic uncertainties, and the uncertainty in bombarding energy and angle. This measurement represents a calibration standard for polarized beams in this energy range. The absolute scale for the measurement has been obtained by comparison with p+C elastic scattering at the same energy at an angle where ${\mathit{A}}_{\mathit{y}}$ is very nearly unity.