Lepton Isolation Using Particle Flow Objects for the ATLAS Detector

This note presents a novel method for isolation using particle flow objects. The study is focused on muon isolation, but it is expected that these techniques would also be applicable for electrons and photons. It will be shown to be robust against pile-up, which is one of the challenges at the LHC. High efficiency in identifying truly isolated particles needs to be balanced by good fake rejection such that non-isolated particles do not pass the isolation criteria. Particle flow isolation shows improvements over previously used track and calorimeter based isolation, preserving a higher fake rejection for a similar isolation efficiency. For an efficiency of 90$\%$, particle flow isolation achieves a fake rejection of 63$\%$ whereas the standard isolation techniques reach only 40$\%$.