UC Berkeley

Searches for the exclusive decays of the Higgs and Z bosons into a J / ψ , ψ ( 2 S ) , or ϒ ( n S ) ( n = 1 , 2 , 3 ) meson and a photon are performed with a pp collision data sample corresponding to an integrated luminosity of 36.1 fb − 1 collected at s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above the expected backgrounds, and 95% confidence-level upper limits on the branching fractions of the Higgs boson decays to J / ψ γ , ψ ( 2 S ) γ , and ϒ ( n S ) γ of 3.5 × 10 − 4 , 2.0 × 10 − 3 , and ( 4.9 , 5.9 , 5.7 ) × 10 − 4 , respectively, are obtained assuming Standard Model production. The corresponding 95% confidence-level upper limits for the branching fractions of the Z boson decays are 2.3 × 10 − 6 , 4.5 × 10 − 6 and ( 2.8 , 1.7 , 4.8 ) × 10 − 6 , respectively.