Search for Dark Matter Produced in Association with a Higgs Boson Decaying to $b\overline{b}$ Using $36{\mathrm{fb}}^{-1}$ of $pp$ Collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS Detector

Several extensions of the standard model predict associated production of dark-matter particles with a Higgs boson. Such processes are searched for in final states with missing transverse momentum and a Higgs boson decaying to a $b\overline{b}$ pair with the ATLAS detector using $36.1{\mathrm{fb}}^{-1}$ of $pp$ collisions at a center-of-mass energy of 13 TeV at the LHC. The observed data are in agreement with the standard model predictions and limits are placed on the associated production of dark-matter particles and a Higgs boson.

Figure 1

Distributions of the invariant mass of the Higgs boson candidates $m_h=m_{jj},m_J$ with two $b$ tags in the SR for the four $E_T^{\mathrm{miss}}$ categories that are used as inputs to the fit. The upper panels show a comparison of data to the SM expectation before (dashed lines) and after the fit (solid histograms) with no signal included. The lower panels display the ratio of data to SM expectations after the fit, with its systematic uncertainty considering correlations between individual contributions indicated by the hatched band. The expected signal from a representative $Z^{\prime }\text{−}2\mathrm{HDM}$ model is also shown (long-dashed line).

Figure 2

Exclusion contours for the $Z^{\prime }\text{−}2\mathrm{HDM}$ scenario in the $(m_{Z^{\prime }},m_A)$ plane for $\tan \beta =1$, $g_{Z^{\prime }}=0.8$, and $m_{\chi }=100\mathrm{GeV}$. The observed limits (solid line) are consistent with the expectation under the SM-only hypothesis (dashed line) within uncertainties (solid band). Observed limits from previous ATLAS results at $\sqrt{s}=13\mathrm{TeV}$ (dash-dotted line) [32] are also shown.