Direct detection of Higgs-portal dark matter at the LHC

Abstract

We consider the process in which a Higgs particle is produced in association with jets and show that monojet searches at the LHC already provide interesting constraints on the invisible decays of a 125 GeV Higgs boson. Using the existing monojet searches performed by CMS and ATLAS, we show the 95% confidence level limit on the invisible Higgs decay rate is of the order of the total Higgs production rate in the Standard Model. This limit could be significantly improved when more data at higher center of mass energies are collected, provided systematic errors on the Standard Model contribution to the monojet background can be reduced. We also compare these direct constraints on the invisible rate with indirect ones based on measuring the Higgs rates in visible channels. In the context of Higgs portal models of dark matter, we then discuss how the LHC limits on the invisible Higgs branching fraction impose strong constraints on the dark matter scattering cross section on nucleons probed in direct detection experiments.

Figures (3)

• Figure 1: The fraction of events with Higgs transverse momentum above a given threshold for the ggF (red circles) and VBF (blue squares) production modes. The distributions were obtained at NLO using the program POWHEGAlioli:2008tz. In the case of ggF, the simulations included the finite quark mass effects Bagnaschi:2011tu, and we find good agreement with the NNLO distribution obtained using the program HResdeFlorian:2012mx (black line).
• Figure 2: $68\%$ CL (light green) and $95\%$ CL (dark green) best fit regions to the combined LHC Higgs data. The black meshed region is excluded by the monojet constraints derived in this paper, while the red meshed region is excluded by the recent ATLAS $Z+(H \rightarrow {\rm MET})$ search ATLAS_Inv.
• Figure 3: Bounds on the spin-independent direct detection cross section $\sigma^{\rm SI}_{\chi p}$ in Higgs portal models derived for $M_H=125$ GeV and the invisible branching fraction of 20 % (colored lines). The curves take into account the full $M_\chi$ dependence, without using the approximation in Eq. \ref{['Eq:brmax']}. For comparison, we plot the current and future direct bounds from the XENON experiment (black lines).