Comment on "Difference betweene+ande−deep-inelastic scattering"

On the basis of a parton model, Fishbane and Kingsley have investigated the difference between $e^{-}p$ and $e^{+}p$ deep-inelastic scattering in the backward direction and found it to be of relative order $\alpha {\ln }^2\left(\frac{Q^2}{{\mu }^2}\right)$, where $\mu$ is a typical hadronic mass. We have reexamined this problem in the more general kinematic region $E_1\gg E_3$ ($E_1$ and $E_3$ are the initial and final electron energies, respectively) and have taken care to distinguish between hard- and soft-photon radiative corrections. The noninfrared part of the virtual photon correction has been found to be of relative order $\alpha {\ln }^2\left(\frac{E_1}{E_3}\right)$. It is hard to conceive of a situation where such a contribution to the cross section would be observable.