Abstract
We investigate a possible realization of pseudo-Nambu-Goldstone (pNG) dark matter in the framework of a singlet-extended 2 Higgs doublet model (S2HDM). pNG dark matter gained attraction due to the fact that direct-detection constraints can be avoided naturally because of the momentum-suppressed scattering cross sections, whereas the relic abundance of dark matter can nevertheless be accounted for via the usual thermal freeze-out mechanism. We confront the S2HDM with a multitude of theoretical and experimental constraints, paying special attention to the theoretical limitations on the scalar potential, such as vacuum stability and perturbativity. In addition, we discuss the complementarity between constraints related to the dark matter sector, on the one hand, and to the Higgs sector, on the other hand. In our numerical discussion we explore the Higgs funnel region with dark matter masses around 60 GeV using a genetic algorithm. We demonstrate that the S2HDM can easily account for the measured relic abundance while being in agreement with all relevant constraints. We also discuss whether the so-called center-of-galaxy excesses can be accommodated, possibly in combination with a Higgs boson at about 96 GeV that can be the origin of the LEP- and the CMS-excess observed at this mass in the b overline{b} -quark and the diphoton final state, respectively.
Highlights
Collaboration [10], using the precise map of the cosmic microwave background (CMB), reports the most precise measurement of today’s DM relic abundance, (Ωh2)Planck = (0.119 ± 0.003)
We investigate a possible realization of pseudo-Nambu-Goldstone dark matter in the framework of a singlet-extended 2 Higgs doublet model (S2HDM). pNG dark matter gained attraction due to the fact that direct-detection constraints can be avoided naturally because of the momentum-suppressed scattering cross sections, whereas the relic abundance of dark matter can be accounted for via the usual thermal freeze-out mechanism
We focus on the S2HDM with type II Yukawa structure and the parameter space that gives rise to the so called Higgs funnel scenario, i.e. resonant DM annihilation via s-channel diagrams mediated by the SM-like Higgs boson h125
Summary
The remaining terms of the scalar potential V involve the singlet field φS and respect a global U(1) symmetry, except for the term proportional to μ2χ. This term softly breaks the U(1) symmetry, providing a non-zero mass for the pNG DM. We verify for each parameter point whether there exists a global minimum of the potential with v1, v2, vS > 0 and vC, vCP, vDM = 0 Otherwise, we remove such a point, since it potentially features an EW vacuum that is short-lived compared to the age of the universe (see section 3.1 for details). The charged scalar sector remains unchanged compared to the 2HDM It contains two physical charged Higgs bosons H± with mass mH± and the charged Goldstone bosons related to the gauge symmetries. The relations between the parameters shown in eq (2.5) and the Lagrangian parameters of the potential in eq (2.2) are given in appendix A
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