Xiao-Gang He, Jusak Tandean
The underground CDMS II experiment searching directly for weakly interacting massive particle (WIMP) dark matter (DM) has observed three WIMP-candidate events corresponding to a WIMP mass of order 9 GeV. Since the confidence level of the finding is only about three sigmas, it does not yet offer conclusive evidence for WIMPs. Nevertheless, interestingly, although the parameter region implied by the signal hypothesis seems to be already excluded mainly by the current strictest limits from the XENON experiments, most of this tension can go away if the WIMP interaction with nuclei violates isospin symmetry. This motivates us to explore some of the implications for models in which a real gauge-singlet scalar particle, dubbed the darkon, serves as the WIMP, taking into account the recent discovery of a Higgs boson at the LHC and Planck determination of the DM relic density. In the simplest scenario, which involves only the standard model plus a darkon, the Higgs boson is largely invisible due to its decay into a pair of darkons having the WIMP mass suggested by CDMS II and hence cannot be identified with the one found at the LHC. We find, on the other hand, that in a two-Higgs-doublet model supplemented with a darkon there is ample parameter space to accommodate well both the new CDMS II and LHC data, whether or not the darkon-nucleon interaction is isospin violating.
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http://arxiv.org/abs/1304.6058
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