Large-angle elastic proton-proton polarization at 5.15GeVc

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 $\frac{\mathrm{GeV}}{c}$ are presented for ${30}^{\circ }\lesssim {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim {90}^{\circ }$. These results, which extend to $t\approx -4.0\mathrm{}{\left(\frac{\mathrm{GeV}}{c}\right)}^2$, represent the first high-statistics $p-p$ polarization measurements for $\mathrm{}\left|t\right|\mathrm{}$ values greater than ∼2.5 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$. We observe a minimum in the polarization near $t=-0.8\mathrm{}{\left(\frac{\mathrm{GeV}}{c}\right)}^2$, a smooth increase in the polarization until a maximum is attained near $t=-1.8\mathrm{}{\left(\frac{\mathrm{GeV}}{c}\right)}^2$, and then a monotonic decline in the polarization until the value of zero is reached at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}={90}^{\circ }$. The data are analyzed in terms of an optical model.