Speaker
Description
Pulsar Timing Arrays (PTAs) have gathered strong evidence for the existence of a Stochastic Gravitational Wave Background at nanohertz frequencies. A possible astrophysical explanation of the signal is the production of Gravitational Waves (GWs) from the merging of Supermassive Black Hole Binaries, but many different explanations, which invoke new physics beyond the Standard Model, have been proposed, such as First Order Phase Transitions (FOPTs).
In this work we will propose a baryogenesis model from a FOPT below a GeV, producing GWs that could explain those recently observed at PTAs. In particular, we consider a darkogenesis mechanism where a fermionic dark matter candidate and a neutron mix via an effective operator and the baryon asymmetry is produced via resonant oscillations between the neutron and dark matter. This idea can be implemented in a model with a dark $U(1)$ gauge symmetry where the mass of the dark photon is generated via a dark Higgs mechanism. The main novelty of this work is that we assume that the potential of the dark Higgs scalar is scale invariant and that its vacuum expectation value (VEV) is generated by radiative corrections at one-loop, as in the Coleman-Weinberg model. The VEV enters in the mass mixing term and, ultimately, in the baryon asymmetry.
This effective potential induces a supercooled FOPT and leads to the generation of GWs. We find that the parameters of our model yielding to successful baryogenesis could also explain the recent GWs observation at PTAs.
