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Hidden $U(1)$ gauge symmetry realizing a neutrinophilic two-Higgs-doublet model with dark matter

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 Added by Takaaki Nomura
 Publication date 2017
  fields
and research's language is English




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We propose a neutrinophilic two Higgs doublet model with hidden local $U(1)$ symmetry, where active neutrinos are Dirac type, and a fermionic DM candidate is naturally induced as a result of remnant symmetry even after the spontaneous symmetry breaking. In addition, a physical Goldstone boson is arisen as a consequence of two types of gauge singlet bosons and contributes to the DM phenomenologies as well as additional neutral gauge boson. Then we will analyze the relic density of DM within the safe range of direct detection searches, and show the allowed region of dark matter mass.



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General Two Higgs Doublet Models (2HDM) are popular Standard Model extensions but feature flavor changing interactions and lack neutrino masses. We discuss a 2HDM where neutrino masses are generated via type I seesaw and propose an extension where neutrino masses are generated via a type II seesaw mechanism with flavor changing interactions being absent via the presence of a U(1) gauge symmetry. After considering a variety of bounds such as those rising from collider and electroweak precision we show that our proposal stands as a UV complete 2HDM with a dark photon where neutrino masses and flavor changing interactions are addressed. A possible dark matter realization is also discussed.
We study a fermionic dark matter model in which the interaction of the dark and visible sectors is mediated by Higgs portal type couplings. Specifically, we consider the mixing of a dark sector scalar with the scalars of a Two Higgs Doublet Model extension of the Standard Model. Given that scalar exchange will result in a spin-independent dark matter-nucleon scattering cross section, such a model is potentially subject to stringent direct detection constraints. Moreover, the addition of new charged scalars introduce non-trivial flavour constraints. Nonetheless, this model allows more freedom than a standard Higgs portal scenario involving a single Higgs doublet, and much of the interesting parameter space is not well approximated by a Simplified Model with a single scalar mediator. We perform a detailed parameter scan to determine the mass and coupling parameters which satisfy direct detection, flavour, precision electroweak, stability, and perturbativity constraints, while still producing the correct relic density through thermal freezeout.
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 degeneracy 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.
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