Gravitational Waves from the Phase Transition of a Non-linearly Realised Electroweak Gauge Symmetry

TL;DR

This paper explores the potential for detecting gravitational waves generated during a strongly first-order electroweak phase transition driven by anomalous Higgs self-couplings in a non-linearly realised Standard Model, with implications for future space-based detectors.

Contribution

It investigates the gravitational wave signatures of a modified electroweak phase transition with anomalous Higgs self-couplings and assesses their detectability by upcoming space-based observatories.

Findings

Gravitational waves in the mHz range could be detected by eLISA.

BBO could detect a wider frequency range of gravitational waves.

Detectability depends on the magnitude of the anomalous Higgs cubic coupling.

Abstract

Within the Standard Model with non-linearly realised electroweak symmetry, the LHC Higgs boson may reside in a singlet representation of the gauge group. Several new interactions are then allowed, including anomalous Higgs self-couplings, which may drive the electroweak phase transition to be strongly first-order. In this paper we investigate the cosmological electroweak phase transition in a simplified model with an anomalous Higgs cubic self- coupling. We look at the feasibility of detecting gravitational waves produced during such a transition in the early universe by future space-based experiments. We find that for the range of relatively large cubic couplings, $111~{\rm GeV}~ \lesssim |\kappa| \lesssim 118~{\rm GeV}$, $\sim $mHz frequency gravitational waves can be observed by eLISA, while BBO will potentially be able to detect waves in a wider frequency range, $0.1-10~$mHz.