Searches for exotic decays of the Higgs Boson to a pair of light resonances with the ATLAS detector

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Exotics decays of the Higgs boson provide a unique window for the discovery of new physics, as the Higgs may couple to hidden-sector states that do not interact under the Standard Model gauge transformations. Models predicting exotic Higgs decays to pseudoscalars can explain the galactic center gamma-ray excess, if the additional pseudoscalar acts as the dark matter mediator. This talk presents recent ATLAS searches for decays of the 125 GeV Higgs boson to a pair of new light bosons, H -> aa, where the a-bosons decay to various final states. These searches use LHC collision data at sqrt(s) = 13 TeV collected by the ATLAS experiment in 2015 and 2016. Upper limits on the branching ratio σ(H)/σ(SM) x Br(H -> aa) are set in the a-boson mass range between 1–60 GeV. Finally, a comparison of other ATLAS search channels is presented to illustrate the strength of each analysis in probing new physics.