# Gravitational waves from scale-invariant vector dark matter model: Probing below the neutrino-floor

## TL;DR

This paper explores gravitational wave signals from a scale-invariant vector dark matter model with a dark U(1) symmetry, showing potential detectability by space-based GW detectors despite some dark matter interactions being below direct detection limits.

## Contribution

It introduces a scale-invariant extension of the Standard Model with a dark U(1) gauge symmetry, analyzing its GW signatures and dark matter detection prospects.

## Key findings

- Strongly first-order electroweak phase transition occurs in the model.
- GW signals from the phase transition are within eLISA's observational window.
- Some dark matter parameter space is below neutrino-floor for direct detection.

## Abstract

We study the gravitational waves (GWs) spectrum produced during the electroweak phase transition in a scale-invariant extension of the Standard Model (SM), enlarged by a dark $ U(1)_{D} $ gauge symmetry. This symmetry incorporates a vector dark matter (DM) candidate and a scalar field (scalon). Because of scale invariance, the model has only two independent parameters and for the parameter space constrained by DM relic density, strongly first-order electroweak phase transition can take place. In this model, for a narrow part of the parameter space, DM-nucleon cross section is below the neutrino-floor limit, and therefore, it cannot be probed by the future direct detection experiments. However, for a benchmark point form this narrow region, we show the amplitude and frequency of phase transition GW spectrum fall within the observational window of space-based GW detectors such as eLISA.