Large-angle elastic proton--proton polarization at 5.15 GeV/c

We present herein the initial results of a large-angle elastic p-p polarization experiment which is now in progress at the Argonne ZGS (Zero-Gradient Synchrotron) accelerator. Data for the incident proton momentum of 5.15 GeV/c are presented for ${30}^{\circ }\lesssim {\theta }_{c.m.}\lesssim {90}^{\circ }$. These results, which extend to t≈-4.0(GeV/c)², represent the first high-statistics p-p polarization measurements for |t| values greater than ∼2.5 (GeV/c)². We observe a minimum in the polarization near t=-0.8(GeV/c)², a smooth increase in the polarization until a maximum is attained near t=-1.8(GeV/c)², and then a monotonic decline in the polarization until the value of zero is reached at ${\theta }_{c.m.}={90}^{\circ }$. The data are analyzed in terms of an optical model.