Majorana dark matter through a narrow Higgs portal

Abstract

We update the parameter space of a singlet Majorana fermion dark matter model, in which the standard particles interact with the dark sector through the mixing of a singlet scalar and the Higgs boson. In this model both the dark matter and the singlet scalar carry lepton number, the latter being a bilepton. The stability of the Majorana fermion is achieved by a supposed Z 2 symmetry. The lepton number symmetry breaking scale, driven by the singlet scalar, is constrained to be within hundreds to thousands of GeV, so as to give a sufficiently abundant Majorana fermion. Relic density, direct detection and invisible Higgs decay are considered in a complementary way, as we contrast our parameter space with the Planck, LUX and LHC bounds. The impacts of the future Higgs self-coupling measurements and of XENON1T detector are also discussed. We find a "narrow" Higgs portal in the sense that large deviations from the standard scalar sector (large mixing and low lepton breaking scale) are very restricted by Higgs data global fit. We perform a systematic study of the allowed parameter space, favored by scalar resonances and degeneracy. One important phenomenological signature of this model is the correlation between the discoveries of a dark matter and a singlet scalar particles. Very light singlet scalars were found disfavored by direct detection, interestingly implying that the Majoron present in our spectrum can hardly be a dark radiation candidate if our scenario addresses the DM issue. This model is very predictive and in the next few years should be completely tested by the experiments.

NLO+NLL collider bounds, Dirac fermion and scalar dark matter in the B–L model

“…Such large couplings arise naturally in 3-3-1 models [28,[71][72][73][74][75][76][77][78] and left-right models [49,52,[79][80][81][82][83][84][85][86]. Other fermion dark matter models feature similar trends [87][88][89][90][91].…”

The waning of the WIMP? A review of models, searches, and constraints

“…The limits from DD experiments are complemented at low DM masses, i.e., m χ,ψ,V < m h /2, by the one from invisible decay width of the Higgs. Indeed this constraint would exclude DM masses below the energy threshold [143,145,[192][193][194][195][196][197][198][199][200][201][202][203][204][205].…”

Long-Lived Light Mediators from Higgs boson Decay at HL-LHC, FCC-hh and a Proposal of Dedicated LLP Detectors for FCC-hh

“…Figs. 23 and 24 shows the projected upper limit on the branching fraction, Br(h → φφ), for the six combinations of cuts for the benchmark masses mentioned above over a range of decay lengths from 0.01 m to 10 4 m, assuming the minimal model defined in eq. (2.1), combined over ggF, VBF, Vh-jet and Vh-lep modes for Figure 23: Projected upper limits on the branching fraction, Br(h → φφ), for 50 observed decays of long-lived mediator particles using the CMS MS when events are selected by applying the four sets of cuts described in the beginning of section 3.1.2.…”

“…On the other hand, the fact that lighter WIMPs have evaded our experiments till now motivates their search further, and it incites us to search for the so-called light mediator particle, which is predicted in many scenarios for light WIMPs and connecting dark sector particles (i.e., dark matter) with those of the SM. For instance, focusing on light fermionic WIMPs, the minimal renormalizable model consistent with Lorentz symmetry requires a bosonic mediator particle connecting the dark matter with the SM [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], where the latter has to be as light as the WIMP to explain the dark matter relic abundance. Moreover, from the viewpoint of the small-scale problems of structure formation in our universe [30], a light fermionic WIMP with a light bosonic mediator enjoys particular attention, since it can potentially solve the problem by generating a large and velocity-dependent scattering cross section between the light WIMPs [31].…”