Searches for exclusive Higgs and Z boson decays into J/ψ γ, ψ(2S) γ, and ϒ(nS) γ at s=13TeV with the ATLAS detector

Abstract

Searches for the exclusive decays of the Higgs and Zbosons into a J/ψ, ψ(2S), or ϒ(nS)(n =1, 2, 3) meson and a photon are performed with a ppcollision data sample corresponding to an integrated luminosity of 36.1fb−1collected at √s=13TeVwith 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/ψγ, ψ(2S) γ, and ϒ(nS) γof 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 Zboson decays are 2.3 ×10−6, 4.5 ×10−6and (2.8, 1.7, 4.8) ×10−6, respectively