Totalp−pand "p−n" Cross Sections at Cosmotron Energies

The total proton-proton cross section (excluding Coulomb scattering) has been measured at energies from 410 Mev up to 2.6 Bev, using external beams from the Cosmotron. Fast counting equipment was used to measure the attenuation of the beams through polyethylene, carbon, and liquid ${\mathrm{H}}_2$ absorbers. At each energy $E$, ${\sigma }_{p-p}(E, \Omega )$ was measured as a function of the solid angle $\Omega$ subtended by the rear counter at the center of the absorber. The total cross section ${\sigma }_{p-p}$ was obtained by a least squares straight line extrapolation to $\Omega =0\mathrm{}$. The measured ${\sigma }_{p-p}$ as a function of energy rises sharply from 26.5 mb at 410 Mev to 47.8 mb at 830 Mev and then remains approximately constant out to 1.4 Bev, above which energy it decreases gradually to about 42 mb at 2.6 Bev.