Wing Sheung Chan

Object reconstruction and identification 63 6 7 8 9 20 30 40 50 60 Efficiency 0.96 0.98 1 ATLAS -1 = 13 TeV, 3.2 fb s |>0.1 η muons, | Medium Data µµ→ψ J/ MC µµ→ψ J/ Data µµ→ Z MC µµ→ Z [GeV] T p 6 7 8 910 20 30 40 50 60 2 10 Data / MC 0.98 1 1.02 Stat only Stat ⊕ Sys (a) Efficiency 0.96 0.98 1 − − − − − 0.6 0.65 ATLAS -1 = 13 TeV, 3.2 fb s Data MC µµ→ Z η 2.5 − 2 − 1.5 − 1 − 0.5 − 0 0.5 1 1.5 2 2.5 Data / MC 0.98 1 1.02 Stat only Stat ⊕ Sys muons Medium | < 0.1) η muons (| Loose (b) [GeV] T p 20 30 40 50 60 70 2 10 2 10 × 2 Efficiency 0.4 0.5 0.6 0.7 0.8 0.9 1 > < 50 µ Data 2017, < > > 50 µ Data 2017, < Preliminary ATLAS -1 = 13 TeV, 32.8 fb s FixedCutTight (c) 2.5 − 2 − 1.5 − 1 − 0.5 − 0 0.5 1 1.5 2 2.5 [GeV] µµ σ 1.5 2 2.5 3 3.5 4 µµ→ Z ATLAS -1 = 13 TeV, 2.7 fb s Data MC Syst. uncert. ) lead µ ( η 2.5 − 2 − 1.5 − 1 − 0.5 − 0 0.5 1 1.5 2 2.5 Data/MC 0.8 1 1.2 (d) Figure 3.7.: The measured (a), (b) reconstruction and identification efficiency, and (c) isolation efficiency of muons with Medium identification and FCTight isolation as functions of the muon transverse momentum or pseudorapidity, and (d) the dimuon in- variant mass resolution for Z → µµ events as a function of the leading- p T muon pseudorapidity [86, 87] . as X invisible p T = − X visible p T ≡ E miss T . (3.10) This is called the missing transverse momentum, with the magnitude and azimuthal angle denoted as E miss T and φ miss respectively. Thanks to the solid angular coverage of almost 4 π , the ATLAS detector is capable of reconstructing E miss T accurately in most scenarios. The E miss T of an event is calculated as the sum of two terms, the “hard term” and the “soft term” [88, 89] . The hard term is the negative vector sum of the transverse momenta of all reconstructed physics objects that have passed certain basic quality requirements. To avoid double counting, objects that are geometrically close to another object are removed