High-energy anomalous scattering: Is it semiclassical?

We discuss the possibility of a semiclassical evaluation of baryon-number-nonconserving scattering amplitudes at ‘‘nonperturbative’’ energies of order ${\mathit{M}}_{\mathit{W}}$/${\mathrm{\alpha }}_{\mathit{W}}$. Semiclassical expansions around standard instanton configurations are known not to be valid at these energies: multiloop radiative corrections are not suppressed relative to tree-graph contributions. Despite this pathology, we present a conjecture showing how anomalous scattering at such nonperturbative energies may nevertheless remain semiclassically calculable, and discuss partial results supporting this conjecture. To determine the correct weak-coupling behavior of high-energy anomalous scattering amplitudes, we argue that one must solve a modified set of classical field equations, or equivalently sum suitably modified tree graphs.