The performance of missing transverse momentum reconstruction and its significance with the ATLAS detector using 140 fb-1 of SQUARE ROOTs = 13 TeV pp collisions

Abstract

This paper presents the reconstruction of missing transverse momentum (pmissT ) in proton-proton collisions, ata center-of-mass energy of 13 TeV. This is a challenging taskinvolving many detector inputs, combining fully calibratedelectrons, muons, photons, hadronically decaying τ -leptons,hadronic jets, and soft activity from remaining tracks. Possibledouble counting of momentum is avoided by applyinga signal ambiguity resolution procedure which rejects detectorinputs that have already been used. Several pmissT 'workingpoints' are defined with varying stringency of selections,the tightest improving the resolution at high pile-up by upto 39% compared to the loosest. The pmissT performance isevaluated using data and Monte Carlo simulation, with anemphasis on understanding the impact of pile-up, primarilyusing events consistent with leptonic Z decays. The studiesuse 140 fb-1 of data, collected by the ATLAS experimentat the Large Hadron Collider between 2015 and 2018. Theresults demonstrate that pmissT reconstruction, and its associatedsignificance, are well understood and reliably modelledby simulation. Finally, the systematic uncertainties on thesoft pmissT component are calculated. After various improvementsthe scale and resolution uncertainties are reduced byup to 76% and 51%, respectively, compared to the previous calculation at a lower luminosity.