UC Irvine

This paper presents a dedicated search for exotic decays of the Higgs boson to a pair of new spin-zero particles, H→aa$$H \rightarrow aa$$, where the particle a decays to b-quarks and has a mass in the range of 20–60 GeV. The search is performed in events where the Higgs boson is produced in association with a W$$W$$ boson, giving rise to a signature of a lepton (electron or muon), missing transverse momentum, and multiple jets from b-quark decays. The analysis is based on the full dataset of pp collisions at s=13TeV$$\sqrt{s} = 13\,\mathrm{{TeV}}$$ recorded in 2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb-1$$\text{ fb }^{-1}$$. No significant excess of events above the Standard Model prediction is observed, and a 95%$$95\,\%$$ confidence-level upper limit is derived for the product of the production cross section for pp→WH$$pp \rightarrow WH$$ times the branching ratio for the decay H→aa→4b$$H \rightarrow aa \rightarrow 4b$$. The upper limit ranges from 6.2 pb for an a-boson mass ma=20GeV$$m_a = 20\,\mathrm{{GeV}}$$ to 1.5 pb for ma=60GeV$$m_a = 60\,\mathrm{{GeV}}$$.