The Higgs-portal for vector dark matter and the effective field theory approach: A reappraisal

Abstract

We reanalyze the effective field theory approach for the scenario in which the particles that account for the dark matter (DM) in the universe are vector states that interact only or mainly through the Standard Model-like Higgs boson observed at the LHC. This model-independent and simple approach, with a minimal set of new input parameters, is widely used as a benchmark in DM searches and studies in astroparticle and collider physics. We show that this effective theory could be the limiting case of ultraviolet complete models, taking as an example the one based on a spontaneously broken U(1) gauge symmetry that incorporates a dark gauge boson and an additional scalar that mixes with the standard Higgs boson. Hence, despite the presence of the new degrees of freedom, measurements of the invisible decay branching ratio of the Higgs boson, as performed at colliders such as the CERN LHC, can be interpreted consistently in such an effective framework and can be made complementary to results of DM searches in direct detection experiments.Particle physics proposes a compelling solution to the puzzle of the missing or dark matter (DM) in the Universe, in terms of a colorless and electrically neutral weakly interacting massive particle (WIMP) that is stable at cosmological times and has a mass in the vicinity of the electroweak scale. Such WIMPs are predicted in many extensions of the Standard Model (SM); for reviews, see Refs. [1,2] for instance. A very interesting class of such models is the one in which the DM states interact only through their couplings with the Higgs sector of the theory, the so-called Higgs-portal DM models; see Ref.[3] for a recent review. The observed cosmological relic abundance would be induced when pairs of DM states annihilate into SM fermions and gauge bosons, through the s-channel exchange of the Higgs bosons, and the latter will in turn be the mediators of the mechanisms that allow for the experimental detection of the DM states.The simplest of the Higgs-portal scenarios is when the Higgs sector is minimal and, thus, identical to the SM one, namely a single doublet Higgs field structure that leads to the unique H boson observed so far [4,5]. One could then minimally extend the model by simply adding one new particle, the DM state, as an isosinglet under the electroweak group. Nevertheless, the DM particle can have the three possible spin assignments and be a scalar, a vector or a Dirac or Majorana spin-1 2 fermion. Although only effective, this approach can be adopted as it is rather model-independent and does not make any assumption on the very nature of the DM [6-15]. Furthermore, it bears the advantage of having a very restricted number of extra parameters in addition to the SM ones [16], namely the mass of the DM particle and its coupling to the Higgs boson.Such a minimal scheme has been investigated extensively and has been probed in direct and indirect detection in astrophysical experiments, and at colliders such as the CERN LHC. In the latter case, light DM particles are searched for...

Heavy dark matter through the dilaton portal

“…The particular challenge for the vector case is to allow it to remain stable; a Z 2 symmetry forbids conventional gauge interactions. We must either accept this [9,[19][20][21][22] or we can stabilise the vector through another symmetry such as a custodial one [23]. Here we shall be considering the minimal model, which can arise from a Stückelberg U(1) field coupled to the dilaton.…”

“…after neglecting any higher-dimensional operators. This can be compared with the standard Higgs-portal Lagrangian for vector dark matter L VHPDM (which has become a popular benchmark scenario) [21,22],…”

The Higgs-portal for dark matter: effective field theories versus concrete realizations

“…A brief discussion of these issues has been recently made in Ref. [15], focusing exclusively on the case of a vector DM candidate interacting with the SM Higgs sector. The EFT approach has been confronted with its simplest UV-completion, namely the one in which the DM state is identified with the stable gauge boson of a dark U(1) gauge symmetry group, spontaneously broken by an extra complex scalar field which develops a vacuum expectation value [16][17][18][19][20][21].…”

“…In the same spirit as in Ref. [15], the predictions in the three realizations of the Higgs-portal effective field theories are compared with those of renormalizable ultraviolet complete models of increasing complexity. First, in the vector DM case, we go beyond the simplest U(1) UV-realization and discuss the possibility of a DM state that belongs to a hidden sector with larger gauge symmetries, namely SU(2) and SU (3).…”

Vector dark matter from split SU(2) gauge bosons

“…Focusing on fundamental DM particles, a simple vector DM model can be constructed by introducing a dark U(1) gauge group with a dark Higgs field providing the gauge boson mass and a portal to the SM sectors [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. A Z 2 symmetry is required to guarantee the stability of the vector DM candidate.…”