Speaker
Description
We investigate an extension of the Standard Model featuring a local $U(1)_X$ gauge symmetry, an additional complex scalar singlet, and two scalar doublets, one of which is inert. The scalar sector consists of an active doublet responsible for electroweak symmetry breaking, an inert doublet that yields a scalar Dark Matter candidate, and a singlet scalar whose vacuum expectation value spontaneously breaks $U(1)_X$. A neutral fermion $\chi$, charged under $U(1)_X$ and even with respect to an imposed $\mathbb{Z}_2$ symmetry, serves as a second, fermionic Dark Matter candidate. The inert doublet is $\mathbb{Z}_2$-odd, ensuring the stability of the scalar dark matter component.
We analyze the scalar and gauge boson mass spectra after spontaneous symmetry breaking, accounting for kinetic mixing and neutral gauge boson mixing. The interactions relevant for Dark Matter annihilation and direct detection are derived, and we examine the relic abundance within a two-component dark matter framework. Both the fermion $\chi$ and the inert scalar can reproduce the observed relic density in complementary regions of parameter space, consistent with current experimental bounds. This framework offers a rich phenomenology, connecting extended gauge dynamics, scalar sector structure, and dark matter physics.