Measurement ofp↑+p↑→p+p with a 16.5-GeV/cpolarized proton beam

Using the new Brookhaven Alternating Gradient Synchrotron polarized proton beam and our polarized proton target, we measured the spin-spin correlation parameter $A_{\mathrm{nn}}$ in 16.5-GeV/c proton-proton elastic scattering. We found an $A_{\mathrm{nn}}$ of (6.1±3.0)% at $P_{\perp }$ ${\mathrm{}}^2$=2.2 (GeV/c${)}^2$. We also measured the analyzing power A in two independent ways, providing a good test of possible experimental errors. Comparing our new data with 12-GeV Argonne Zero Gradient Synchrotron data shows no evidence for strong energy dependence in $A_{\mathrm{nn}}$ in this medium-$P_{\perp }$ ${\mathrm{}}^2$ region.