Nonleading Energy Behavior and the Breaking of Scale Invariance inνW2

Abstract

A recently proposed Regge model for describing the general features of on- and off-shell Compton scattering, using a simple form of scale-invariance breaking in $q^2$, is discussed and confronted with recent data. It is suggested that the mass size characteristic of the scale-invariance breaking is indicative, as well, of the relative contributions of the Pomeranchukon, $f-A_2$, and additional nonleading power behavior. The observed rapid approach to "scaling" in $q^2$ (at given $\nu$) is seen to require a small characteristic mass which in turn requires a substantial nonleading contribution to the scaling function $\nu W_2$. Continuation of the resulting form to on-shell scattering predicts a nonleading power contribution to ${\sigma }_{\mathrm{tot}}\left(\gamma p\right)$; a recent continuous-moment sum-rule analysis is consistent with this prediction.