A search for prompt lepton-jets in $pp$ collisions at $\sqrt{s}=$ 8 TeV with the ATLAS detector

TL;DR

This paper reports a search for a hypothetical light boson decaying into collimated leptons in proton-proton collisions at 8 TeV, using ATLAS data, finding no evidence for such particles and setting upper limits on their production.

Contribution

The study introduces a novel search for light bosons decaying into lepton-jets in ATLAS data, constraining models like SUSY-portal and Higgs-portal.

Findings

No significant excess observed over Standard Model predictions.

Set 95% confidence level upper limits on new physics contributions.

Constrained parameter space for light boson models.

Abstract

A search is presented for a new, light boson with a mass of about 1 GeV and decaying promptly to jets of collimated electrons and/or muons (lepton-jets). The analysis is performed with 20.3 fb$^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider in proton--proton collisions at a centre-of-mass energy of 8 TeV. Events are required to contain at least two lepton-jets. This study finds no statistically significant deviation from predictions of the Standard Model and places 95\% confidence-level upper limits on the contribution of new phenomena beyond the SM, incuding SUSY-portal and Higgs-portal models, on the number of events with lepton-jets.