Photonucleon Total Cross Sections at Very High Energy

Abstract

Photon-neutron total cross sections have been evaluated from the data for the proton and deuteron presented in the preceding paper. Simple Regge-pole fits have been made to ${\sigma }_T\left(\gamma p\right)$ and ${\sigma }_T\left(\gamma n\right)$, both of which extrapolate to 94 ± 4 μb at infinite energy. Over the range of our data, 3.7 to 17.9 GeV, ${\sigma }_T\left(\gamma n\right)<\mathrm{}{\sigma }_T\left(\gamma p\right)$, which can be interpreted to give a ratio of exchange contributions, $\frac{A_2}{P^{\prime }}=0.19\mathrm{}\pm 0.04$. A fit to ${\sigma }_T\left(\gamma p\right)$ is also important for predictions of the proton cosmic-ray spectrum.