We measured the analyzing power A and the spin-spin correlation parameter A nn , in large-Pi proton-proton elastic scattering, using a polarized-proton target and the polarized-proton beam at the Brookhaven Alternating-Gradient Synchrotron. We also used our polarimeter to measure A at small P] at 13 GeV with good precision and found some deviation from the expected 1/P| ab behavior. At 18.5 GQV/C we found A m = ( -2 ± 16)% at P\ =4.7 (GeV/c) 2 . Comparison with lower-energy data from the Argonne Zero-Gradient Synchrotron shows a sharp and surprising energy dependence for A m at large P\.

No abstract