0.8 GeVp+Pb208elastic scattering and the quantityΔrnp

Analyses of 0.8 and 1 GeV $p$+${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ elastic angular distribution data have obtained neutron-proton root-mean-square radius differences ($\Delta r_{\mathrm{np}}$) which are not consistent. Therefore, the 0.8 GeV experiment was repeated using a high resolution spectrometer. The new higher precision data are consistent with the older data, apart from a 15% overall normalization difference. A second order Kerman-McManus-Thaler optical model analysis of the new data, using a model-independent neutron density, yields $\Delta r_{\mathrm{np}}=0.14\mathrm{}\pm 0.04$ fm, in good agreement with the most recent result obtained (0.16±0.05 fm) from a similar analysis of the older 0.8 GeV data. In addition, the elastic angular distribution was extended to 42.5° center of mass in order to explore the momentum transfer region from 3.5 to 5.3 ${\mathrm{fm}}^{-1\mathrm{}}$. Although the familiar diffraction pattern persists to 42.5°, it was not possible within the framework of our application of the Kerman-McManus-Thaler optical model to fit the data even qualitatively at the larger momentum transfers.