Abstract

Searches for exclusive decays of the Higgs boson into D-0 gamma and of the Z boson into D-0 gamma and K-s(0)gamma can probe flavour-violating Higgs boson and Z boson couplings to light quarks. Searches for these decays are performed with a pp collision data sample corresponding to an integrated luminosity of 136.3 fb(-1) collected at root s=13TeV between 20162018 with the ATLAS detector at the CERN Large Hadron Collider. In the D*gamma and D-0 gamma channels, the observed (expected) 95% confidence-level upper limits on the respective branching fractions are B(H -> D*gamma)<1.0(1.2)x10(-3), B(Z -> D-0 gamma)<4.0(3.4)x10(-6), while the corresponding results in the K-s(0)gamma channel are B(Z -> K-s(0)gamma)<3.1(3.0)x10(-6)