Abstract
We propose and study a scalar extension of the Standard Model which respects a ℤ3 symmetry remnant of the spontaneous breaking of a global U(1)DM symmetry. Consequently, this model has a natural dark matter candidate and a Goldstone boson in the physical spectrum. In addition, the Higgs boson properties are changed with respect to the Standard Model due to the mixing with a new particle. We explore regions in the parameter space taking into account bounds from the measured Higgs properties, dark matter direct detection as well as measurements of the effective number of neutrino species before recombination. The dark matter relic density is determined by three classes of processes: the usual self-annihilation, semi-annihilation and purely dark matter 3 → 2 processes. The latter has been subject of recent interest leading to the so-called `Strongly Interacting Massive Particle' (SIMP) scenario. We show under which conditions our model can lead to a concrete realization of such scenario and study the possibility that the dark matter self-interactions could address the small scale structure problems. In particular, we find that in order for the SIMP scenario to work, the dark matter mass must be in the range 7−115 MeV, with the global symmetry energy breaking scale in the TeV range.
Highlights
In this paper we explore an intermediate situation, where a global U(1)dark matter (DM) symmetry is spontaneously broken to a discrete Z3 symmetry by postulating the existence of a scalar field with charge 3 under the global group and a non-vanishing vacuum expectation value [29]
We have presented a scalar extension of the Standard Model (SM) consisting of two additional complex fields with charges one and three under a global U(1)DM symmetry
The nonzero vacuum expectation value of the latter field spontaneously breaks the global symmetry down to a remnant Z3. This leads to the appearance of a Goldstone boson (GB), two Higgs-like particles, one of which is identified with the SM scalar, and a complex field that, due to the discrete symmetry, can not decay and is a candidate for dark matter (DM)
Summary
We postulate a dark sector with a global U(1)DM which is spontaneously broken into a Z3 symmetry. The potential in eq (2.3) is manifestly invariant under the remnant Z3 ⊂ U(1)DM that acts non-trivially only on the field X in the following way: X → It is precisely because of this reason that the particle associated to X can not decay and is identified with the DM. Where we identify h with the SM Higgs boson with mass mh ∼ 125 GeV and the mixing angle θ is defined by tan 2θ λφH vH vφ λφ vφ2 − λH vH2. We will use the following parameters to characterize the model: two masses (mρ and mX ), the mixing angle θ and five quartic couplings λφ, λX , λ3, λφX and λHX. The model was implemented in FeynRules [32, 33] and the output was used both in CalcHEP [34] and MicrOMEGAs [35, 36] in the phenomenological studies discussed
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