Dark matter particles, if sufficiently light, may be produced in decays of the Higgs boson. This Letter presents a statistical combination of searches for $H\to \text{invisible}$ decays where $H$ is produced according to the standard model via vector boson fusion, $Z(\ell \ell )H$, and $W/Z(\mathrm{had})H$, all performed with the ATLAS detector using $36.1{\mathrm{fb}}^{-1}$ of $pp$ collisions at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ at the LHC. In combination with the results at $\sqrt{s}=7$ and 8 TeV, an exclusion limit on the $H\to \text{invisible}$ branching ratio of $0.26(0.17_{-0.05}^{+0.07})$ at 95% confidence level is observed (expected).

• Received 11 April 2019

DOI:https://doi.org/10.1103/PhysRevLett.122.231801

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© 2019 CERN, for the ATLAS Collaboration