Dark matter and dark force in the type-I inert 2HDM with local U(1) H gauge symmetry

Abstract

We discuss dark matter (DM) physics in the Type-I inert two-Higgs-doublet model (2HDM) with local U(1) H Higgs gauge symmetry, which is assigned to the extra Higgs doublet in order to avoid the Higgs-mediated flavor problems. In this gauged inert DM setup, a U(1) H -charged scalar Φ is also introduced to break U(1) H spontaneously through its nonzero vacuum expectation value (VEV), Φ , and then the remnant discrete subgroup appears according to the U(1) H charge assignment of Φ. The U(1) H -charged Higgs doublet does not have Yukawa couplings with the Standard-Model (SM) fermions, and its lightest neutral scalar component H is stable because of the remnant discrete symmetry. In order to suppress a too large Z-exchange diagram contribution in DM direct detection experiments, we have to introduce a non-renormalizable operator which can be generated by integrating out an extra heavy scalar. With these new particles contents, we first investigate the constraint on the U(1) H gauge interaction, especially through the kinetic and mass mixing between the SM gauge bosons and the extra gauge boson. Then we discuss dark matter physics in our 2HDM: thermal relic density, and direct/indirect detections of dark matter. The additional U(1) H gauge interaction plays a crucial role in reducing the DM thermal relic density. The most important result within the inert DM model with local U(1) H symmetry is that ∼ O(10) GeV dark matter scenario, which is strongly disfavored in the usual Inert Doublet Model (IDM) with Z 2 symmetry, is revived in our model because of newly open channels, HH → Z H Z H , Z H Z. Exotic Higgs decays, h → Z H Z H , ZZ H , would be distinctive signatures of the inert 2HDM with local U(1) H symmetry.

G2HDM: Gauged Two Higgs Doublet Model

“…The popular choice is a discrete symmetry, such as Z 2 on the second Higgs doublet in IHDM or 2HDM type-I [22,23], type-II [23,24], type-X and type-Y [25][26][27] where some of SM fermions are also odd under Z 2 unlike IHDM. The other choice is a continuous symmetry, such as a local U(1) symmetry discussed in [28][29][30][31]. The FCNC constraints can be avoided by satisfying the alignment condition of the Yukawa couplings [32] to eliminating dangerous tree-level contributions although it is not radiatively stable [33].…”

Higgs and dark matter physics in the type-II two-Higgs-doublet model inspired by E 6 GUT

“…[14]. Also they constructed the inert 2HDM model with U(1) H gauge symmetry and showed that the light dark matter (DM) mass region below ∼ m W is widely open if the Z 2 symmetry is implemented into local U(1) H gauge symmetry, due to newly open annihilation channels of the DM pair into the extra U(1) H gauge boson(s): HH → Z H Z H , ZZ H , which are not present in the ordinary inert 2HDM with discrete Z 2 symmetry [18]. In fact this phenomenon is very generic in dark matter models with local dark gauge symmetries [19][20][21][22][23][24].…”

“…On the other hand, some of them might be stable (or long-lived enough) and could be good cold dark matter (CDM) candidates as pointed out in refs. [15,18]. Their stability could be guaranteed by the remnant symmetry of U(1) H [18].…”

Neutrino masses in a two Higgs doublet model with a U(1) gauge symmetry

“…Nevertheless, some proposals to extend the 2HDM via the presence of gauge symmetries have been put forth [43][44][45]. Some were triggered by anomalies in flavor and collider physics [46][47][48] and others devoted to explain neutrino masses via type I seesaw mechanism and absence of flavor changing interactions [49][50][51][52].…”