Abstract
Abstract: Measurements and searches performed with the ATLAS detector at the CERN LHC often
involve signatures with one or more prompt leptons. Such analyses are subject to ‘fake/non-prompt’
lepton backgrounds, where either a hadron or a lepton from a hadron decay or an electron from
a photon conversion satisfies the prompt-lepton selection criteria. These backgrounds often arise
within a hadronic jet because of particle decays in the showering process, particle misidentification
or particle interactions with the detector material. As it is challenging to model these processes with
high accuracy in simulation, their estimation typically uses data-driven methods. Three methods
for carrying out this estimation are described, along with their implementation in ATLAS and their
performance.