Search for light long-lived neutral particles produced in pp collisions at $$\sqrt{s} = 13~\mathrm {TeV}$$ and decaying into collimated leptons or light hadrons with the ATLAS detector

Several models of physics beyond the Standard Model predict the existence of dark photons, light neutral particles decaying into collimated leptons or light hadrons. This paper presents a search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1 fb^{-1}collected in...