Visible and dark matter from a first-order phase transition in a baryon-symmetric universe

TL;DR

This paper proposes a model where a first-order phase transition in the early universe creates equal and opposite asymmetries in visible and dark matter, explaining their similar abundances and predicting observable collider signatures.

Contribution

It introduces a novel framework linking dark and visible matter asymmetries through a first-order phase transition, including a specific viable model with testable collider predictions.

Findings

Dark matter is atomic and asymmetric in the model.

The model predicts a Z' boson coupling to B-L charge.

Cosmological and astrophysical constraints are satisfied.

Abstract

The similar cosmological abundances observed for visible and dark matter suggest a common origin for both. By viewing the dark matter density as a dark-sector asymmetry, mirroring the situation in the visible sector, we show that the visible and dark matter asymmetries may have arisen simultaneously through a first-order phase transition in the early universe. The dark asymmetry can then be equal and opposite to the usual visible matter asymmetry, leading to a universe that is symmetric with respect to a generalised baryon number. We present both a general structure, and a precisely defined example of a viable model of this type. In that example, the dark matter is atomic as well as asymmetric, and various cosmological and astrophysical constraints are derived. Testable consequences for colliders include a Z' boson that couples through the B-L charge to the visible sector, but also decays invisibly to dark sector particles. The additional scalar particles in the theory can mix with the standard Higgs boson and provide other striking signatures.