A search for prompt lepton-jets in $pp$ collisions at $sqrts=7$ TeV with the ATLAS detector

Abstract

We present a search for a light (mass < 2 GeV) boson predicted by Hidden Valley supersymmetric models that decays into a final state consisting of collimated muons or electrons, denoted _s15lepton-jets_s15. The analysis uses 5fb-1 of sqrt(s) = 7 TeV proton--proton collision data recorded by the ATLAS detector at the Large Hadron Collider to search for the following signatures: single lepton-jets with at least four muons_s19 pairs of lepton-jets, each with two or more muons_s19 and pairs of lepton-jets with two or more electrons. This study finds no statistically significant deviation from the Standard Model prediction and places 95% confidence-level exclusion limits on the production cross section times branching ratio of light bosons for several parameter sets of a Hidden Valley model.