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

P. Ko 0 1 2 4 5 Yuji Omura 0 1 2 3 5 Chaehyun Yu 0 1 2 4 5 0 Open Access , c The Authors 1 of newly open channels , HH 2 Seoul 130-722 , Korea 3 Department of Physics, Nagoya University 4 School of Physics , KIAS 5 [53] XENON10 collaboration, J. Angle et al., A search for light dark matter in XENON10 data 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 is also introduced to break U(1)H spontaneously through its nonzero vacuum expectation value (VEV), hi, and then the remnant discrete subgroup appears according to the U(1)H charge assignment of . 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 Z2 symmetry, is revived in our model because would be distinctive signatures of the inert 2HDM with local U(1)H symmetry. 1 Introduction 2 2HDM with U(1)H Higgs symmetry 3 4 Mass mixing and kinetic mixing at the one-loop level Constraints on ZH coupling from the mixings Constraints on the extra scalar bosons Constraints from exotic SM-like Higgs decays How to stabilize dark matter in the IDMwU(1)H General conditions for DM stability Toward the IDMwU(1)H DM phenomenology in IDMwU(1)H Relic density and direct detection Constraints from indirect detection The case of IDM with Z2 symmetry The case of IDM with local U(1)H symmetry The case of the IDM with Z2 symmetry The case of IDM with local U(1)H symmetry Three benchmark points for illustration The discovery of a Standard-Model-like Higgs boson at the LHC [1, 2] opens new era in particle physics and cosmology. The precise measurements of its mass and couplings to the Standard Model (SM) particles will reveal the structure of the Higgs sector, which is the least known piece in the SM. Up to now, its couplings to the ordinary particles are consistent with the predictions of the SM within uncertainties and most of results at the LHC can be understood in the framework of the SM [3, 4]. On the other hand, there are some clues on new physics beyond the SM: nonbaryonic dark matter (DM), dark energy, neutrino oscillation, baryon asymmetry of the universe, and etc., which cannot be explained by the renormalizable SM and require its extensions beyond the SM. One simple extension of the SM is to add one extra Higgs doublet. In fact, many highenergy theories predict extra Higgs doublets, and the two-Higgs-doublet models (2HDMs) could be interpreted as the effective theories of those high energy theories after we integrate out heavy particles. Of course, the 2HDMs could be interesting by themselves, because of their rich phenomenology and benchmark models with an extended Higgs sector. 2HDMs predict extra neutral and charged scalar bosons in addition to a SM-like Higgs boson, and the extra scalar bosons may change phenomenology of Higgs boson and SM particles at We could also find cold dark matter candidates in some 2HDMs: one of the extra scalars [69] or one of the extra fermions, which may be added to the models in 2HDMs with gauged U(1)H symmetry [10]. When the Higgs potential in 2HDMs has a CPviolating source, the baryon asymmetry of the universe may be explained [11]. And small neutrino masses may naturally be generated by one-loop diagram in some 2HDMs [12]. Finally, it is very interesting that in 2HDMs with flavor-dependent U(1)H gauge symmetry, the anomalies in the top forward-backward asymmetry at the Tevatron and B D() decays at BABAR may be reconciled [1318]. One important phenomenological issue in models with extra Higgs doublets is the socalled Higgs-mediated flavor changing neutral current (FCNC) problem. If a right-handed (RH) fermion couples with more than two Higgs doublets, FCNCs involving the neutral scalar bosons generally appear after the electro-weak (EW) symmetry breaking. In many cases, this Higgs-mediated flavor problem is resolved by imposing softly-broken Z2 symmetry a la Glashow and Weinberg [19]. The discrete Z2 symmetry could be replaced by other discrete symmetry [20] or continuous local gauge symmetry [10]. In fact, the present authors proposed a new class of 2HDMs where U(1)H Higgs gauge symmetry is introduced instead of softly broken discrete Z2 symmetry, in order to avoid the flavor problem [10], and discussed the phenomenology of Type-I 2HDM with U(1)H in ref. [21]. When Higgs ated from the SM prediction at the tree level if the U(1)H -charged Higgs doublet develops a nonzero vacuum expectation value (VEV). In ref. [21], the authors investigate the constraints not only from the EW precision observables (EWPOs) but also from the recent LHC results on the SM-like Higgs search, especially in Type-I 2HDMs where only one Higgs doublet is charged and the SM particles are neutral under U(1)H . The deviation gauge boson (ZH ), and from the mass differences among the scalar bosons. The bounds on EWPOs require small U(1)H interactions, so that its effects become tiny in physical In this work, we consider a new scenario where the VEV of the U(1)H -charged Higgs spontaneously. In this case, the mass mixing between gauge bosons is also negligible at the tree level. Therefore we can expect that the ZH gauge interaction becomes sizable and then the idea of gauged U(1)H Higgs symmetry might be tested. The bounds on ZH mass and its couplings to the SM particles will come from the loop-level mass and kinetic mixings between the SM gauge bosons and ZH , as well as the tree-level kinetic mixing. On the other hand, the SM fermions are chiral under new U(1)H gauge symmetry, so that the model may be anomalous unless new chiral fermions are introduced. As discussed in refs. [10, 21], we could consider the anomaly-free U(1)H charge assignment to build the 2HDM with local Higgs symmetry: for example, the SM particles are not charged and only one extra Higgs doublet is charged under U(1)H . In our 2HDM, the U(1)H will be (...truncated)