Search for Higgs boson decays into a pair of light bosons in the $bb\mu\mu$ final state in $pp$ collision at $\sqrt{s} = $13 TeV

A search for Higgs boson pair production in the $b\bar{b}WW^{\ast}$ decay mode is performed in the $b\bar{b}\ell\nu qq$ final state using 36.1 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of events beyond the background expectation is found. Upper limits on the non-resonant $pp \to HH$ production cross section of 10 pb and on the resonant production cross section as a function of the $HH$ invariant mass are obtained. Resonant production limits are set for scalar and spin-2 graviton hypotheses in the mass range 500 to 3000 GeV.