Coupling WW, ZZ unitarized amplitudes to $\gamma\gamma$ in the TeV region

TL;DR

This paper develops a unitarized amplitude framework linking the Electroweak Symmetry Breaking Sector to gamma gamma processes at TeV energies, enabling the study of resonances and their decays in a consistent, unitarity-preserving manner.

Contribution

It introduces a method to compute and unitarize helicity partial-wave amplitudes connecting EWSBS to gamma gamma, extending HEFT to higher energies and including resonance descriptions.

Findings

Amplitudes satisfy unitarity for all energies.

Framework describes resonance decays into WW, ZZ, and gamma gamma.

Applicable in the 500 GeV to 3 TeV energy range.

Abstract

We define and calculate helicity partial-wave amplitudes for processes linking the Electroweak Symmetry Breaking Sector (EWSBS) to $\gamma\gamma$, employing (to NLO) the Higgs-EFT (HEFT) extension of the Standard Model and the Equivalence Theorem, while neglecting all particle masses. The resulting amplitudes can be useful in the energy regime ($500\,{\rm GeV}-3\,{\rm TeV}$). We also deal with their unitarization so that resonances of the EWSBS can simultaneously be described in the $\gamma\gamma$ initial or final states. Our resulting amplitudes satisfy unitarity, perturbatively in $\alpha$, but for all $s$ values. In this way we improve on the HEFT that fails as interactions become stronger with growing $s$ and provide a natural framework for the decay of dynamically generated resonances into $WW$, $ZZ$ and $\gamma\gamma$ pairs.