Abstract
We investigate the indirect signatures of the Higgs portal U(1)X vector dark matter (VDM) Xμ from both its pair annihilation and decay. The VDM is stable at renormalizable level by Z2 symmetry, and thermalized by Higgs-portal interactions. It can also decay by some nonrenormalizable operators with very long lifetime at cosmological time scale.If dim-6 operators for VDM decays are suppressed by 1016 GeV scale, the lifetime of VDM with mass ∼ 2 TeV is just right for explaining the positron excess in cosmic ray observed by PAMELA and AMS02 Collaborations. The VDM decaying into μ+μ− can fit the data, evading various constraints on cosmic rays. We give one UV-complete model as an example. This scenario for Higgs portal decaying VDM with mass around ∼ 2 TeV can be tested by DM direct search at XENON1T, and also at the future colliders by measuring the Higgs self-couplings.
Highlights
We investigate the indirect signatures of the Higgs portal U (1)X vector dark matter (VDM) Xμ from both its pair annihilation and decay
If we assume that (i) these positron excess is due to the decaying VDM of mass ∼ 2 TeV which were thermalized by Higgs portal interaction [16], and (ii) the EW vacuum is stable up to the scale Λ where the operators for VDM decays [16], we find that the most parameter region could be probed by the future experiments for direct detection of WIMP’s in the mass range ∼ 2 TeV
Since our aim is to explain the positron excess observed by PAMELA and AMS02 in terms of VDM
Summary
We consider a vector dark matter (VDM), Xμ, which is associated with an Abelian dark gauge symmetry U (1)X implemented with discrete Z2 symmetry Xμ → −Xμ. The simplest renormalizable and unitary model would be the one with an extra complex scalar Φ, whose vacuum expectation value (vev) is responsible for the mass of Xμ [16]: L. The mass matrix of two scalar bosons in the basis (h, φ) can be written in terms of either Lagrangian parameters or the physical parameters as follows: M≡. MH2 1 c2α + MH2 2 s2α MH2 2 − MH2 1 sαcα MH2 2 − MH2 1 sαcα MH2 1 s2α + MH2 2 c2α This renormalizable Lagrangian for the Higgs portal VDM model, Eq (2.1), has four more parameters compared with the SM: λΦ, vvΦ, gX and λHΦ. Since our aim is to explain the positron excess observed by PAMELA and AMS02 in terms of VDM decays, we will concentrate mainly on heavy VDM with mass around a few TeV in this paper.
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