Electroweak Chiral Lagrangians and $\gamma\gamma\to Z_L Z_L,\, W_L^+ W_L^-$ at One Loop

TL;DR

This paper calculates one-loop corrections to gamma-gamma to W and Z boson scattering within electroweak chiral Lagrangians with a light Higgs, providing insights into potential physics beyond the Standard Model.

Contribution

It performs the first next-to-leading order computation of these processes in the effective field theory, showing the amplitudes are UV finite and identifying additional observables for global fits.

Findings

One-loop amplitudes are ultraviolet finite.

Relevant chiral couplings do not run at this order.

Additional observables depend on the same parameters for global analysis.

Abstract

In these proceedings we discuss our recent work on $\gamma\gamma\to W^+_L W^-_L$ and $\gamma\gamma\to Z_L Z_L$ within the framework of Electroweak Chiral Lagrangians with a light Higgs. These observables are good candidates to provide indications of physics beyond the Standard Model and can complement other analyses and global fits. Making use of the equivalence theorem, we have performed the computation up to the next-to-leading order in the chiral expansion, i.e., including one-loop corrections and the full set of possible counterterms allowed at that order in the low-energy effective field theory. The one-loop amplitudes turn out to have a extremely simple structure and they are ultraviolet finite. Thus, the relevant combinations of higher order chiral couplings $c_\gamma^r$ and $(a_1^r-a_2^r+a_3^r)$ do not run. We also identify an additional set of observables that depend on these same parameters, which can be use to complement the $\gamma\gamma$ analysis through a global fit.