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We consider a Higgs portal model in which the 125-GeV Higgs boson mixes with a light singlet mediator $h_2$ coupling to particles of a Dark Sector and study potential $bto s h_2$ decays in the Belle II experiment. Multiplying the gauge-dependent off-shell Standard-Model $b$-$s$-Higgs vertex with the sine of the Higgs mixing angle does not give the correct $b$-$s$-$h_2$ vertex. We clarify this issue by calculating the $b$-$s$-$h_2$ vertex in an arbitrary $R_xi$ gauge and demonstrate how the $xi$ dependence cancels from physical decay rates involving an on-shell or off-shell $h_2$. Then we revisit the $bto s h_2$ phenomenology and point out that a simultaneous study of $Bto K^* h_2$ and $Bto K h_2$ helps to discriminate between the Higgs portal and alternative models of the Dark Sector. We further advocate for the use of the $h_2$ lifetime information contained in displaced-vertex data with $h_2$ decaying back to Standard-Model particles to better constrain the $h_2$ mass or to reveal additional $h_2$ decay modes into long-lived particles.
The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the dominant interactions of gauge bosons and the physical Higgs particle $h$ to a scalar singlet dark matter can
We review scenarios in which the particles that account for the Dark Matter (DM) in the Universe interact only through their couplings with the Higgs sector of the theory, the so-called Higgs-portal models. In a first step, we use a general and model
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 ext
Fermion dark matter (DM) interacting with the standard model through a Higgs portal requires non-renormalizable operators, signaling the presence of new mediator states at the electroweak scale. Collider signatures that involve the mediators are a po
Supersymmetric (SUSY) extension of the Standard Model (SM) is a primary candidate for new physics beyond the SM. If SUSY breaking scale is very low, for example, the multi-TeV range, and the SUSY breaking sector, except for the goldstino (gravitino),