Abstract
We construct a model based on an extra gauge symmetry, SU(2)_X x U(1)_{B-L}, which can provide gauge bosons to serve as weakly-interacting massive particle dark matter. The stability of the dark matter is naturally guaranteed by a discrete Z_2 symmetry that is a subgroup of SU(2)_X. The dark matter interacts with standard model fermions by exchanging gauge bosons which are linear combinations of SU(2)_X x U(1)_{B-L} gauge bosons. With the appropriate choice of representation for the new scalar multiplet whose vacuum expectation value spontaneously breaks the SU(2)_X symmetry, the relation between the new gauge boson masses can naturally lead to resonant pair annihilation of the dark matter. After exploring the parameter space of the new gauge couplings subject to constraints from collider data and the observed relic density, we use the results to evaluate the cross section of the dark matter scattering off nucleons and compare it with data from the latest direct detection experiments. We find allowed parameter regions that can be probed by future direct searches for dark matter and LHC searches for new particles.
Highlights
Of the Z′-exchange contributions to the relic density. All this motivates us to look for a different possible scenario in which the resonance condition can be fulfilled naturally. We demonstrate that such a possibility can be realized in a model where the role of WIMP DM is played by massive gauge bosons associated with a nonabelian symmetry
Since SM fermions are charged under U(1)B−L, the DM can interact with SM fermions at tree level by exchanging gauge bosons which are obtained from the linear combinations of SU(2)X and U(1)B−L gauge fields
In this paper we have constructed a model possessing an extra gauge symmetry, SU(2)X ×U(1)B−L, which offers a massive gauge boson, X, associated with SU(2)X playing the role of WIMP DM
Summary
Compared to the SM, the new model contains the additional gauge group SU(2)X ×U(1)B−L, where X refers to the massive gauge boson that serves as the DM,. In table 1 we collect the SU(2)X ×U(1)B−L quantum number assignments for the fermions, scalars, and new gauge bosons in the model, with H being the usual scalar doublet. After SU(2)X ×U(1)B−L spontaneously breaks into Z2X ×Z2B−L, the new gauge bosons acquire in L the mass terms. For an SU(2)X isospin value TX and its third component T3X , one would get m2X /m2ZL ≃ TX (TX + 1) − T32X / 2T32X assuming small mixing angle θ, in analogy to the ρ parameter in the electroweak sector [1]. Since X is our chosen candidate for DM and interacts with SM fermions by exchanging the ZL,H bosons at tree level, in the following two sections we evaluate the new gauge couplings subject to collider and relic density data. We use the allowed values of the couplings to predict the cross section of the DM-nucleon scattering and compare it with the existing results of DM direct detection experiments
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