We propose to investigate a secluded WIMP dark matter model consisting of neutral fermions as the dark matter candidate and a Proca-Wentzel (PW) field as a mediator. In the model that we consider here, dark matter WIMPs interact with standard model (
SM) particles only through the PW field of ~ MeV -- multi-GeV mass particles. The interactions occur via an U(1) mediator, V_{mu}, which couples to the SM by kinetic mixing with U(1) hypercharge bosons, B_{mu}. One important difference between our model and other such models in the literature is the absence of an extra singlet scalar, so that the parameter with dimension of mass M^2_V is not related to a spontaneous symmetry breaking. This QED based model is also renormalizable. The mass scale of the mediator and the absence of the singlet scalar can lead to interesting astrophysical signatures. The dominant annihilation channels are different from those usually considered in previous work. We show that the GeV-energy gamma-ray excess in the galactic center region, as derived from Fermi-LAT Gamma-ray Space Telescope data, can be attributed to such secluded dark matter WIMPs, given parameters of the model that are consistent with the cosmological dark matter density. Secluded WIMP models are also consistent with suggested upper limits on the DM contribution to the cosmic-ray antiproton flux.
We consider the decays $htogammagamma,gamma Z$ in the context of an extension of the standard model with two inert doublets and an additional $S_3$ symmetry. This model has contributions for these processes through new charged scalar-loops. Comparing
our $htogammagamma$ with the more precise available experimental data we can predict the behaviour of $htogamma Z$ due that they depend on the same parameters, our estimation for this channel is 1.05 times the standard model value, but can be up to 1.16 if consider the $+1sigma$ uncertainty from the $htogammagamma$ data, and down to 0.96 if consider $-1sigma$.
We study a two scalar inert doublet model (IDMS$_3$) which is stabilized by a $S_3$ symmetry. We consider two scenarios: i) two of the scalars in each charged sector are mass degenerated due to a residual $Z_2$ symmetry, ii) there is no mass degenera
cy because of the introduction of soft terms that break the $Z_2$ symmetry. We show that both scenarios provide good dark matter candidates for some range of parameters.
