Abstract
We consider a standard model extension equipped with a dark sector where the U(1)X Abelian gauge symmetry is spontaneously broken by the dark Higgs mechanism. In this framework, we investigate patterns of the electroweak phase transition as well as those of the dark phase transition, and examine detectability of gravitational waves (GWs) generated by such strongly first order phase transition. It is pointed out that the collider bounds on the properties of the discovered Higgs boson exclude a part of parameter space that could otherwise generate detectable GWs. After imposing various constraints on thi model, it is shown that GWs produced by multi-step phase transitions are detectable at future space-based interferometers, such as LISA and DECIGO, if the dark photon is heavier than 25 GeV. Furthermore, we discuss the complementarity of dark photon searches or dark matter searches with the GW observations in these models with the dark gauge symmetry.
Highlights
We consider a standard model extension equipped with a dark sector where the U(1)X Abelian gauge symmetry is spontaneously broken by the dark Higgs mechanism
We explore the Higgs portal DM model with vector DM (VDM), which is stabilized by introducing a discrete Z2, and investigate the complementarity of the detection of gravitational waves (GWs) from the strongly 1stOPT, collider bounds and DM searches
In order to discuss GWs originating from the first order EWPT in an analytic manner, we introduce several important quantities that parametrize the dynamics of vacuum bubbles following ref
Summary
As discussed in refs. [45, 46, 48], there are typically four different types of PT path as shown in figure 1. In order to discuss GWs originating from the first order EWPT in an analytic manner, we introduce several important quantities that parametrize the dynamics of vacuum bubbles following ref. The transition temperature Tt is defined such that the bubble nucleation probability per Hubble volume per Hubble time reaches the unity:. The produced GWs are enhanced as the released energy density ǫ is increased. A dimensionless parameter α is defined as the ratio of ǫ to the radiation energy density ρrad = (π2/30)g∗T 4 at the transition temperature Tt: α ǫ(Tt) ρrad(Tt). We employ the approximate analytic formula provided in ref. [85] for computing the spectrum of the GWs We employ the approximate analytic formula provided in ref. [85] for computing the spectrum of the GWs
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