Hidden Photon and Axion Dark Matter from Symmetry Breaking

TL;DR

This paper investigates the production of light hidden photon and axion-like dark matter through symmetry breaking dynamics, highlighting the role of parametric resonance and phase transition order in determining their abundance and potential gravitational wave signals.

Contribution

It provides a detailed analysis of dark Higgs dynamics during phase transitions, incorporating portal couplings and thermal effects, to explain dark matter abundance and predict observable gravitational waves.

Findings

Efficient production of Nambu-Goldstone bosons via parametric resonance at symmetry breaking.

Dark matter abundance can be explained for sub eV axion or hidden photon masses.

First order phase transition scenarios may produce detectable gravitational waves.

Abstract

A light hidden photon or axion-like particle is a good dark matter candidate and they are often associated with the spontaneous breaking of dark global or gauged U(1) symmetry. We consider the dark Higgs dynamics around the phase transition in detail taking account of the portal coupling between the dark Higgs and the Standard Model Higgs as well as various thermal effects. We show that the (would-be) Nambu-Goldstone bosons are efficiently produced via a parametric resonance with the resonance parameter $q\sim 1$ at the hidden symmetry breaking. In the simplest setup, which predicts a second order phase transition, this can explain the dark matter abundance for the axion or hidden photon as light as sub eV. Even lighter mass, as predicted by the QCD axion model, can be consistent with dark matter abundance in the case of first order phase transition, in which case the gravitational wave signals may be detectable by future experiments such as LISA and DECIGO.