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 "lepton-jets". The analysis uses 5 fb(-1) of root 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; pairs of lepton-jets, each with two or more muons; 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.

A search for prompt lepton-jets in pp collisions at with the ATLAS detector

BELLAGAMBA, LORENZO;BERTIN, ANTONIO;BOSCHERINI, DAVIDE;BRUNI, ALESSIA;BRUNI, GRAZIANO;CAFORIO, DAVIDE;DE CASTRO, STEFANO;DI SIPIO, RICCARDO;FABBRI, LAURA;FRANCHINI, MATTEO;GIACOBBE, BENEDETTO;MASSA, IGNAZIO GIACOMO;MENGARELLI, ALBERTO;MONZANI, SIMONE;PICCININI, MAURIZIO;RINALDI, LORENZO;ROMANO, MARINO;SBARRA, CARLA;SBRIZZI, ANTONIO;