Study of Majorana Fermionic Dark Matter

We construct a generic model of Majorana fermionic dark matter (DM). Starting with two Weyl spinor multiplets $η_{1,2}\sim (I,\mp Y)$ coupled to the Standard Model (SM) Higgs, six additional Weyl spinor multiplets with $(I\pm 1/2, \pm(Y\pm 1/2))$ are needed in general. It has 13 parameters in total, five mass parameters and eight Yukawa couplings. The DM sector of the minimal supersymmetric standard model (MSSM) is a special case of the model with $(I,Y)=(1/2,1/2)$. Therefore, this model can be viewed as an extension of the neutralino DM sector. We consider three typical cases: the neutralino-like, the reduced and the extended cases. For each case, we survey the DM mass $m_χ$ in the range of $(1,2500)$ GeV by random sampling from the model parameter space and study the constraints from the observed DM relic density, the direct search of LUX, XENON100 and PICO experiments, and the indirect search of Fermi-LAT data. We investigate the interplay of these constraints and the differences among these cases. It is found that the direct detection of spin-independent DM scattering off nuclei and the indirect detection of DM annihilation to $W^+W^-$ channel are more sensitive to the DM searches in the near future. The allowed mass for finding $\tilde H$-, $\tilde B$-, $\tilde W$- and non neutralino-like DM particles and the predictions on $\langleσ(χχ\rightarrow ZZ, ZH, t{\bar t}) v\rangle$ in the indirect search are given.

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