Suppression of Electroweak Instanton Processes in High-energy Collisions

TL;DR

This paper reviews electroweak instanton processes in high-energy collisions and demonstrates that quantum effects cause an exponential suppression of their cross section, making observation unlikely.

Contribution

It provides a comprehensive calculation of the electroweak instanton cross section using the optical theorem, including initial state interactions, showing suppression at all energies.

Findings

Electroweak instanton processes are exponentially suppressed at all energies.

Quantum effects from initial state interactions reinforce suppression.

Electroweak instantons remain unobservable in current collider experiments.

Abstract

Electroweak instantons are a prediction of the Standard Model and have been studied in great detail in the past although they have not been observed. Earlier calculations of the instanton production cross section at colliders revealed that it was exponentially suppressed at low energies, but may grow large at energies (much) above the sphaleron mass. Such calculations faced difficulty in the breakdown of the instanton perturbation theory in the high-energy regime. In this paper we review the calculation for the electroweak instanton cross section using the optical theorem, including quantum effects arising from interactions in the initial state and show that this leads to an exponential suppression of the cross section at all energies, rendering the process unobservable.