Spontaneous Electro-Weak Symmetry Breaking and Cold Dark Matter

In the standard model, the weak gauge bosons and fermions obtain mass after spontaneous electro-weak symmetry breaking, which is realized by one fundamental scalar field, namely the Higgs field. We study the simplest scalar cold dark matter model in which the scalar cold dark matter also obtains mass by interaction with the weak-doublet Higgs field, in the same way as those of weak gauge bosons and fermions. Our study shows that the correct cold dark matter relic abundance within 3σ uncertainty (0.093 <Ω_dm h² < 0.129) and experimentally allowed Higgs boson mass (114.4≤ m_h ≤ 208GeV) constrain the scalar dark matter mass within 48≤e m_S ≤78GeV. This result is in excellent agreement with the result of de Boer et al. (50～100GeV). Such a kind of dark matter annihilation can account for the observed gamma rays excess (10σ) at EGRET for nergies above 1GeV in comparison with the expectations from conventional Galactic models. We also investigate other phenomenological consequences of this model. For example, the Higgs boson decays dominantly into scalar cold dark matter if its mass lies within 48～64GeV.