Search for new light gauge bosons in Higgs decays to four-lepton events at s√s=8 TeV with the ATLAS detector

This study presents a search for Higgs bosons decaying to four leptons via one or two light exotic gauge bosons $Z_d$, $H\rightarrow ZZ_d\rightarrow4\ell$ and $H\rightarrow Z_dZ_d\rightarrow4\ell$. The search uses the data taken in $pp$ collisions with the ATLAS detector at the LHC at $\sqrt{s}=8$~TeV. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratios of $H\rightarrow ZZ_d\rightarrow4\ell$ and $H\rightarrow Z_dZ_d\rightarrow4\ell$, relative to the branching ratio of $H\rightarrow 4\ell$ and to the Standard Model branching ratio of $H\rightarrow ZZ^*\rightarrow4\ell$ respectively, are set as a function of the mass of the exotic vector boson at 95\% confidence level.