The small-angle elastic scattering for $\mathrm{pp}$ at $\sqrt{s}=23.5, 30.7, \mathrm{and} 52.8$ GeV and for $\overline{p}p$ at $\sqrt{s}=52.8\mathrm{}$ GeV are measured. The data are normalized on Coulomb scattering. Using the optical theorem and the best estimate of the real part of the forward scattering amplitude, $\rho \left(p\overline{p}\right)=0.1\mathrm{}$, we obtain ${\sigma }_{\mathrm{tot}}\left(\overline{p}p\right)=44.1\mathrm{}\pm 2.9$ mb for the total cross section and $b\left(\overline{p}p\right)=13.6\mathrm{}\pm 2.2$ ${\mathrm{GeV}}^{-2\mathrm{}}$ for the nuclear slope parameter. This supports the dispersion relation prediction that ${\sigma }_{\mathrm{tot}}\left(\overline{p}p\right)$ will start to rise above $E_{\mathrm{lab}}\approx 200$ GeV.

• Received 8 September 1981

DOI:https://doi.org/10.1103/PhysRevLett.47.1191