Spin correlation measurements for p

Abstract

The spin correlation parameter ${\mathit{A}}_{00\mathit{N}\mathit{N}}$ for 497.5 MeV proton + proton elastic scattering was determined over the center-of-momentum scattering angle region 23.1\ifmmode^\circ\else\textdegree\fi{}--64.9 \ifmmode^\circ\else\textdegree\fi{}. The new ${\mathit{A}}_{00\mathit{N}\mathit{N}}$ extend to more forward angles than existing ${\mathit{A}}_{00\mathit{N}\mathit{N}}$ and have significantly smaller statistical errors (\ifmmode\pm\else\textpm\fi{}0.01--0.04). The ${\mathit{A}}_{00\mathit{N}\mathit{N}}$ are qualitatively described by recent phase shift analyses, but a quantitative shape and normalization discrepancy remains in the forward angle region. These new data provide important constraints for nucleon-nucleon spin-dependent amplitudes at forward angles which are used in theoretical models of nucleon-nucleus scattering.