Search for long-lived neutral particles decaying into Lepton-Jets with the ATLAS detector in proton-proton collision data at √s= 13 TeV

Several models of elementary particle physics Beyond the Standard Model predict the existence of neutral particles that can also be long lived and decay in collimated jets of light leptons and hadrons (lepton-jets). The present contribution collects the results about the displaced lepton-jet search with the ATLAS experiment at the proton-proton LHC collider at $\sqrt{s}$=13 TeV during the 2015 data taking period ($3.4 \thinspace \mathrm{fb^{−1}}$). The results are interpreted in terms of the \textit{Falkowsky-Ruderman-Volansky-Zupan models} where dark photons are generated through the decay of a Higgs boson, produced via gluon-fusion. The selected events are compared with the Standard Model expectations and with Beyond Standard Model predictions.