Searching for rare and forbidden exclusive Higgs boson decays with the Atlas detector
Searches for Higgs and Z bosons decaying to an ฯ meson and a photon, and for Higgs bosons decaying to a K(^โ) and a photon are discussed using proton collision data recorded by the ATLAS experiment at โs = 13 TeV between 2016 and 2018. The observed events are consistent with the expected background. The obtained 95% confidence level upper limit on the branching ratio for the H โ ฯฮณ decay using 89.5 fb(^{โ1}) of data is 1.0 ร10(^{โ4}) assuming a Standard Model Higgs Boson production. The analogous limit obtained for the Z โ ฯฮณ decay is 3.5 ร10({โ7}). The obtained upper limit for the H โ K(^โ)ฮณ decay is 8.9 ร10(^{โ5}), using 134 fb(^{โ1}) of data. The search for H โ K(^โ)ฮณ represents the first search for a flavour-violating exclusive decay of the Higgs boson.