Hidden Higgs Boson at the LHC and Light Dark Matter Searches

Abstract: Recent LHC searches have not found a clear signal of the Higgs boson h of the standard model (SM) with three or four families in the mass range m_h = 120-600 GeV. If the Higgs had an unexpectedly large invisible branching ratio, the excluded m_h regions would shrink. This can be realized in the simplest weakly interacting massive particle dark matter (DM) model, which is the SM plus a real gauge-singlet scalar field D as the DM, via the invisible mode h -> DD. Current data allow this decay to occur for D-mass values near, but below, m_h/2 and those compatible with the light DM hypothesis. For such D masses, h -> DD can dominate the Higgs width depending on m_h, and thus sizable portions of the m_h exclusion zones in the SM with three or four families may be recovered. Increased luminosity at the LHC may even reveal a Higgs having SM-like visible decays still hiding in the presently disallowed regions. The model also accommodates well the new possible DM hints from CRESST-II and will be further tested by improved data from future DM direct searches.