Investigating the Sources of Mismeasured Missing Transverse Energy in Simulated Z + 1 jet dilepton decays

We investigate the sources of mismeasured Missing Transverse Energy (MET) in ATLAS Run II Monte Carlo (MC) simulations, specifically looking at events in the tail of the MET distribution where the reconstructed MET is often significantly greater than the truth MET of the simulation. We find the inclusion of jets not associated with the hard physics vertex (pile-up jets) in the MET to be the main cause of mismeasured MET in the tails of Z + jets events and propose a cut using the Jet Tracker Vertex variable (JVT) to remove these jets.