Abstract
We consider a renormalizable extension of the standard model whose fermionic dark matter (DM) candidate interacts with a real singlet pseudo-scalar via a pseudo-scalar Yukawa term while we assume that the full Lagrangian is CP-conserved in the classical level. When the pseudo-scalar boson develops a non-zero vacuum expectation value, spontaneous CP-violation occurs and this provides a CP-violated interaction of the dark sector with the SM particles through mixing between the Higgs-like boson and the SM-like Higgs boson. This scenario suggests a minimal number of free parameters. Focusing mainly on the indirect detection observables, we calculate the dark matter annihilation cross section and then compute the DM relic density in the range up to mDM = 300 GeV.We then find viable regions in the parameter space constrained by the observed DM relic abundance as well as invisible Higgs decay width in the light of 125 GeV Higgs discovery at the LHC. We find that within the constrained region of the parameter space, there exists a model with dark matter mass mDM ∼ 38 GeV annihilating predominantly into b quarks, which can explain the Fermi-LAT galactic gamma-ray excess.
Highlights
The search for deciphering the identity of the dark matter (DM) has been under intense scrutiny since long ago, see reviews in [1, 2]
The former approach relies on the DM scattering with ordinary matter while the latter avenue depends on the dark matter annihilation processes
Our numerical probe over the full parameter space shows that DM scattering rate in our model is far below the minimum bands imposed on the scattering rate by the current results from LUX and XENON100, so that the dark matter particle can evade direct detection
Summary
The search for deciphering the identity of the dark matter (DM) has been under intense scrutiny since long ago, see reviews in [1, 2]. Motivated by the null result from direct detection of DM, it has been thought that the WIMP dark matter may interact in such a way as to leave a trace in one experiment but not necessarily in another one. One example in this regards, is a model put forward in [23] suggesting a new type of dark matter dubbed, coy dark matter. In [24, 25] the possibility of having no signature from direct detection is studied with singlet fermionic dark matter whose interaction with the SM particles is through a Higgs portal.
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