Search for invisible decays of a Higgs boson using vector-boson fusion in pp collisions at s = 8 √s=8 TeV with the ATLAS detector

A search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb -1 of proton-proton collision data at a centreof-mass energy of 8 TeV recorded by the ATLAS detector at the LHC. For a Higgs boson with a mass of 125 GeV, assuming the Standard Model production cross section, an upper bound of 0.28 is set on the branching fraction of H invisible at 95% confidence level, where the expected upper limit is 0.31. The results are interpreted in models of Higgsportal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter-nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments.