First order electroweak phase transition triggered by the Higgs portal vector dark matter

We investigate an extension of the Standard Model (SM) with a $U(1{)}^{\prime }$ gauge symmetry, which is spontaneously broken by a complex scalar singlet and where the new gauge boson is a stable dark matter candidate via a $Z_2$ flavor symmetry. The possibility of generating a strongly first order electroweak phase transition (EWPT) needed for the electroweak baryogenesis mechanism in this model is studied using a gauge-independent method. Our result shows a considerable parameter space where both successful dark matter phenomenologies and a strongly first order electroweak phase transition can be achieved.

Figure 1

Spin-independent dark matter nucleon scattering cross section as the function of the dark matter mass. We set $m_s=320\mathrm{GeV}$ and $v_s=1\mathrm{TeV}$. All the points in blue color give the correct dark matter relic density. The red solid line is the limit of LUX.

Figure 2

${\lambda }_2$ as the function of the dark matter mass. All the points give the correct dark matter relic density. Points in gray color are excluded by the LUX (left panel), points in blue (left panel) and magenta color (right panel) are allowed by the LUX.

Figure 3

$\overline{v}(T_C)/T_C$ as the function of the critical temperature. Points in red color give a correct dark matter relic density and satisfy the LUX constraint in the meanwhile. Points in gray are inconsistent with the constraint of dark matter observables.

Figure 4

$\overline{v}(T_C)/T_C$ as the function of the dark matter mass (left panel) and as the function of the coupling ${\lambda }_2$ (right panel). All the points in red give a correct dark matter relic density and satisfy the LUX constraint in the meanwhile. The points in gray are excluded by the LUX.