Constraining dark matter in the LRTH model with latest LHC, XENON100 and LUX data

In the left-right twin Higgs (LRTH) model, the neutral $\hat{S}$ is a candidate for weakly interacting massive particle (WIMP) dark matter (DM). If its mass is lighter than half of the SM-like Higgs boson $h$, the new invisible decay $h \to \hat{S}\hat{S}$ will become open. In this paper, we examine the status of a light dark matter ($\hat{S}$) under current experimental constraints including the latest LHC Higgs data, the XENON100 and LUX limit on the dark matter scattering off the nucleon. The following observations have been obtained: (i) The current ATLAS (CMS) measurements of $R_{\gamma\gamma}$ can exclude the invisible Higgs branching ratio ${\rm Br}_{\rm inv}$ larger than $34\%$ ($48\%$) at $2\sigma$ level; (ii) the Global fits to the latest LHC and Tevatron Higgs data provide a stronger constraint: ${\rm Br}_{\rm inv}< 20\%$ ($30\%$) at $2\sigma$ ($3\sigma$) level, which could be tested in the LHC experiments; (iii) for the spin-independent scattering cross section off the nucleon, the recent XENON100 (LUX) data can exclude the invisible decay rate larger than $50\%$ $(25\%)$; and (iv) the results of direct DM searches with LUX can give strong constraint on the viable parameter space of $\{g_{h\hat{S}\hat{S}}, m_{\hat{S}}\}$ in this LRTH model.