Abstract
The performance of the missing transverse momentum (E_{mathrm{T}}^{mathrm{miss}}) reconstruction with the ATLAS detector is evaluated using data collected in proton–proton collisions at the LHC at a centre-of-mass energy of 13 TeV in 2015. To reconstruct E_{mathrm{T}}^{mathrm{miss}}, fully calibrated electrons, muons, photons, hadronically decaying tau text {-leptons}, and jets reconstructed from calorimeter energy deposits and charged-particle tracks are used. These are combined with the soft hadronic activity measured by reconstructed charged-particle tracks not associated with the hard objects. Possible double counting of contributions from reconstructed charged-particle tracks from the inner detector, energy deposits in the calorimeter, and reconstructed muons from the muon spectrometer is avoided by applying a signal ambiguity resolution procedure which rejects already used signals when combining the various E_{mathrm{T}}^{mathrm{miss}} contributions. The individual terms as well as the overall reconstructed E_{mathrm{T}}^{mathrm{miss}} are evaluated with various performance metrics for scale (linearity), resolution, and sensitivity to the data-taking conditions. The method developed to determine the systematic uncertainties of the E_{mathrm{T}}^{mathrm{miss}} scale and resolution is discussed. Results are shown based on the full 2015 data sample corresponding to an integrated luminosity of 3.2~hbox {fb}^{-1}.
Highlights
The missing transverse momentum (ETmiss) is an important observable serving as an experimental proxy for the transverse momentum carried by undetected particles produced in proton–proton collisions measured with the ATLAS detector [1] at the Large Hadron Collider (LHC)
Excluding inner detector (ID) tracks associated with any of the accepted hard objects contributing to ETmiss, ID tracks from the hardscatter collision vertex are used to construct the soft-event signal for the results presented in this paper
The level of agreement between the ETmiss distributions for data and Monte Carlo (MC) simulations shown in Fig. 3a for the inclusive event sample is at ±20%, similar to that observed for the Z → μμ sample in Fig. 1a, except that for this final state it is found to be within the total uncertainties of the measurement
Summary
The missing transverse momentum (ETmiss) is an important observable serving as an experimental proxy for the transverse momentum carried by undetected particles produced in proton–proton (pp) collisions measured with the ATLAS detector [1] at the Large Hadron Collider (LHC) It is reconstructed from the signals of detected particles in the final state. ATLAS has developed successful strategies for a high-quality ETmiss reconstruction focussing on the minimisation of effects introduced by pile-up for the data recorded between 2010 and 2012 (LHC Run 1) [2,3] These approaches are the basis for the ETmiss reconstruction developed for the data collected in 2015 (LHC Run 2) that is described in this paper, together with results from performance evaluations and the determination of systematic uncertainties. An evaluation of the effect of alternative jet selections on the ETmiss reconstruction performance is given in Appendix C
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