Can WIMP dark matter overcome the nightmare scenario?

Even if new physics beyond the standard model indeed exists, the energy scale of new physics might be beyond the reach at the Large Hadron Collider (LHC), and the LHC could find only the Higgs boson but nothing else. This is the so-called “nightmare scenario.” On the other hand, the existence of the dark matter has been established from various observations. One of the promising candidates for thermal relic dark matter is a stable and electric charge-neutral weakly interacting massive particle (WIMP) with mass below the TeV scale. In the nightmare scenario, we introduce a WIMP dark matter singlet under the standard model gauge group, which only couples to the Higgs doublet at the lowest order, and investigate the possibility that such WIMP dark matter can be a clue to overcome the nightmare scenario via various phenomenological tests such as the dark matter relic abundance, the direct detection experiments for the dark matter particle, and the production of the dark matter particle at the LHC.

Figure 1

Feynman diagrams for dark matter annihilation.

Figure 2

Constraints on the nightmare scenario from WMAP, Xenon100 first data, and CDMS-II experiments. Higgs mass is fixed to be 120 GeV in left three figures, while 150 GeV in right three figures. Expected sensitivities to detect the signal of the dark matter at XMASS, SuperCDMS, Xenon100, and LHC experiments are also shown in these figures. See the text for the detail of the region painted by dark cyan (light gray).

Figure 3

Cross section of the dark matter signal at the LHC with and without kinematical cuts in Eq. (20). The parameter $m_h$ and $c_{\mathrm{DM}}$ are fixed as shown in these figures.