No Arabic abstract
We propose a minimal model that can explain the electroweak scale, neutrino masses, Dark Matter (DM), and successful inflation all at once based on the multicritical-point principle (MPP). The model has two singlet scalar fields that realize an analogue of the Coleman-Weinberg mechanism, in addition to the Standard Model with heavy Majorana right-handed neutrinos. By assuming a $Z_2 $ symmetry, one of the scalars becomes a DM candidate whose property is almost the same as the minimal Higgs-portal scalar DM. In this model, the MPP can naturally realize a saddle point in the Higgs potential at high energy scales. By the renormalization-group analysis, we study the critical Higgs inflation with non-minimal coupling $xi |H|^2 R$ that utilizes the saddle point of the Higgs potential. We find that it is possible to realize successful inflation even for $xi=25$ and that the heaviest right-handed neutrino is predicted to have a mass around $10^{14}$ GeV to meet the current cosmological observations. Such a small value of $xi$ can be realized by the Higgs-portal coupling $lambda_{SH}simeq 0.32$ and the vacuum expectation value of the additional neutral scalar $langlephiranglesimeq 2.7$ TeV, which correspond to the dark matter mass 2.0 TeV, its spin-independent cross section $1.8times10^{-9}$ pb, and the mass of additional neutral scalar 190 GeV.
Since the current evidence of its existence is revealed only through its gravitational influence, the way dark matter couples to gravity must be then of primary importance. Here, unlike the standard model sector which is typically coupled to metric, dark matter is supposed to couple only to spacetime affine connection through a $Z_2$-symmetry breaking term. We show that this structure leads to a coupling between dark matter, which is considered scalar, and the standard model Higgs potential. This induces dark matter decays into standard model particles through the Higgs which acts as a portal between the visible and the dark sectors. We study thoroughly the resulting decay modes for various mass ranges, and provide relevant bounds on the nonminimal coupling to affine gravity in line with observational data. Moreover, we find that the coupling to Higgs can be sufficiently large to facilitate production of dark matter lighter than 10 GeV at current and future high energy colliders.
We propose a simple scenario that directly connects the dark matter (DM) and neutrino mass scales. Based on an interaction between the DM particle $chi$ and the neutrino $ u$ of the form $chichi u u/Lambda^2$, the DM annihilation cross section into the neutrino is determined and a neutrino mass is radiatively induced. Using the observed neutrino mass scale and the DM relic density, the DM mass and the effective scale $Lambda$ are found to be of the order MeV and GeV, respectively. We construct an ultraviolet-complete toy model based on the inverse seesaw mechanism which realizes this potential connection between DM and neutrino physics.
We explore the scalar phenomenology of a model of electroweak scale neutrinos that incorporates the presence of a lepton number violating singlet scalar. An analysis of the pseudoscalar-Majoron field associated to this singlet field is carried out in order to verify the viability of the model and to restrict its parameter space. In particular we study the Majoron decay $J to u u$ and use the bounds on the Majoron mass and width obtained in a modified Majoron Decaying Dark Matter scenario.
We consider a classically scale-invariant extension of the standard model in which a dark, non-Abelian gauge symmetry is spontaneously broken via the Coleman-Weinberg mechanism. Higgs portal couplings between the dark and standard model sectors provide an origin for the Higgs mass squared parameter and, hence, the electroweak scale. We find that choices for model parameters exist in which the dark gauge multiplet is viable as dark matter.
We consider a renormalizable theory, which successfully explains the number of Standard Model (SM) fermion families and whose non-SM scalar sector includes an axion dark matter as well as a field responsible for cosmological inflation. In such theory, the axion gets its mass via radiative corrections at one-loop level mediated by virtual top quark, right handed Majorana neutrinos and SM gauge bosons. Its mass is obtained in the range $4$ keV$div$ $40$ keV, consistent with the one predicted by XENON1T experiment, when the right handed Majorana neutrino mass is varied from $100$ GeV up to $350$ GeV, thus implying that the light active neutrino masses are generated from a low scale type I seesaw mechanism. Furthermore, the theory under consideration can also successfully accommodates the XENON1T excess provided that the PQ symmetry is spontaneously broken at the $10^{10}$ GeV scale.