Search for Long-lived Particles and Lepton-Jets with the ATLAS detector

Many extensions of the Standard Model (SM) include neutral weakly-coupled particles that can be long-lived. These long-lived particles occur in many models, included gauge-mediated extensions of the Minimal Supersymmetric Model (MSSM), MSSM with R-parity violation, inelastic dark matter and the Hidden Valley (HV) scenario. Results are presented on the ATLAS searches at the LHC for possible rare Higgs boson decays to pair of neutral, long-lived hidden-sector particles that lead to final states containing collimated lepton jets (LJ) or fermion anti-fermion pairs. No excess of events above the expected background has been observed on data collected in 2011 at a center of mass energy of 7 TeV and limits on the cross sections are set.