A search is conducted for a beyond-the-Standard-Model boson using events where a Higgs boson with mass 125 GeV decays to four leptons (ℓ = e or μ). This decay is presumed to occur via an intermediate state which contains one or two on-shell, promptly decaying bosons: H → ZX/XX → 4ℓ, where X is a new vector boson Zdor pseudoscalar a with mass between 1 and 60 GeV. The search uses pp collision data collected with the ATLAS detector at the LHC with an integrated luminosity of 36.1 fb−1at a centre-of-mass energy s=13 TeV. No significant excess of events above Standard Model background predictions is observed; therefore, upper limits at 95% confidence level are set on modelindependent fiducial cross-sections, and on the Higgs boson decay branching ratios to vector and pseudoscalar bosons in two benchmark models.[Figure not available: see fulltext.].

Aaboud, M., Aad, G., Abbott, B., Abdinov, O., Abeloos, B., Abidi, S.H., et al. (2018). Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at √s=13 TeV. JOURNAL OF HIGH ENERGY PHYSICS, 2018(6) [10.1007/JHEP06(2018)166].

Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at √s=13 TeV

Ceradini, F.;Di Micco, B.;Di Nardo, R.;Orestano, D.;