How Big Can Anomalous W Couplings Be?

TL;DR

This paper investigates the potential size of anomalous gauge-boson couplings, challenging the conventional limit of about one percent by computing them in a generic new physics model at one loop.

Contribution

It provides a detailed analysis of the maximum possible size of anomalous W couplings in generic models, including heavy and weak-scale new physics, with implications for experimental detection.

Findings

Couplings can reach several percent at the weak scale.

Heavy new physics generally induces smaller couplings.

Patterns of induced couplings reflect underlying physics.

Abstract

Conventional wisdom has it that anomalous gauge-boson self-couplings can be at most a percent or so in size. We test this wisdom by computing these couplings at one loop in a generic renormalizable model of new physics. (For technical reasons we consider the CP-violating couplings here, but our results apply more generally.) By surveying the parameter space we find that the largest couplings (several percent) are obtained when the new particles are at the weak scale. For heavy new physics we compare our findings with expectations based on an effective-lagrangian analysis. We find general patterns of induced couplings which robustly reflect the nature of the underlying physics. We build representative models for which the new physics could be first detected in the anomalous gauge couplings.