Factorization Theorems for High Energy nn, gamma p and gamma gamma Scattering

The robustness of the factorization theorem for total cross sections, ${\sigma }_{nn}\mathrm{/}{\sigma }_{\gamma p}={\sigma }_{\gamma p}\mathrm{/}{\sigma }_{\gamma \gamma }$, originally proved by Block and Kaidalov\cite{bk} for $nn$ (the even portion of $pp$ and $\text{pbar}p$ scattering), $\gamma p$ and $\gamma \gamma$ scattering, is demonstrated. Factorization theorems for the nuclear slope parameter $B$ and $\rho$, the ratio of the real to the imaginary portion of the forward scattering amplitude, are derived under very general conditions, using analyticity and the optical theorem.