Fermions, Anomaly and Unitarity in High-Energy Electroweak Scattering

TL;DR

This paper reviews the current understanding of B+L violation in high-energy electroweak scattering, focusing on instanton effects, unitarity constraints, and the potential for unsuppressed cross sections at high energies.

Contribution

It provides a comprehensive review of techniques and conceptual issues related to B+L violation, highlighting the possibility of at least partial suppression persisting at high energies.

Findings

Evidence suggests B+L violation cross section remains suppressed by instanton action.

Review of techniques for analyzing anomalous cross sections in electroweak processes.

Discussion of unitarity constraints and conceptual challenges with the optical theorem in instanton contexts.

Abstract

We report the "state of the art" of the problem of $B+L$ violation in high-energy electroweak scatterings. Results of various analyses point toward (though do not prove rigorously yet) the "half-suppression", i.e., that the $B+L$ violating cross section remains suppressed at least by the negative exponent of the single instanton action, at all energies. Most interesting techniques developed in this field are reviewed. Particular attention is paid to unitarity constraints on the anomalous cross section, and to some conceptual problem involving the use of the optical theorem in the presence of instantons.