5. Measurement of the Muon Reconstruction Efficiency 37
5.5. Systematic uncertainties
Background contributions and the finite resolution of the detector lead to systematic uncertainties. Contributions from the latter are estimated by varying the selection cuts when determining the efficiency from Monte–Carlo. The cuts on the mass window around theZ mass and the cut on the transverse momentum of the tag are each varied within their resolution. Other cuts are varied by ±10 % representing a conservative estimate on their precision. The resulting change in the scale factors is quoted as systematic uncertainty. The amount of simulated background is varied by ±10 % and the resulting differences in the scale factors are considered as additional systematic uncertainties.
A variation of ±10 % is chosen as it corresponds to the statistical uncertainty of the measurement of like-charge tag-and-probe pairs presented in section 5.3. Furthermore, the uncertainty of the measurement of electro-weak and QCD background contributions in [68] also state an uncertainty of∼10 %.
The systematic uncertainties on the total scale factors for combined muons are sum-marised in Tab. 5.4. The individual systematic uncertainties are considered to be un-correlated and are added in quadrature to obtain the total systematic uncertainty. For values which result from an up- and downward variation the larger value is quoted and used. The largest deviation arises from the variation of the mass window followed by the variation of the background contamination and the variation of the probe isolation.
As the same tag-and-probe selection is used for the measurement of the CB+ST muon efficiency, the same systematic uncertainties are expected for the corresponding scale factors.
3Feet, transistion and BEE region
4Results obtained by E. Le M´en´edeu in collaboration with the MCP group
5The Staco quality cuts (cf. sec. 5.2) are necessary to suppress secondary muons from decays in flight which are picked up by Staco in 2010 data. These cuts are no longer needed with the improved configuration of Staco in 2011.
46
5.5. Systematic uncertainties
Cut Variation absolute difference of SF from nominal Staco SF = 0.9806 Muid SF = 0.9918
Probe isolation 0.2 → 0.18 0.0009 0.0009
Mass window 10 GeV/c2 → 8 GeV/c2 0.0014 0.0013
∆φ 2.0 → 2.2 0.0003 0.0003
pT(tag) 20 GeV/c → 22 GeV/c 0.0006 0.0006
Probe TRT outlier frac. 0.9 → 0.7 0.0001 0.0001
MC Background + 10% 0.0007 0.0008
Total 0.0020 0.0019
Table 5.4.: Contributions to the total systematic uncertainty in the CB muon efficiency measurement. For the total uncertainty only the largest deviation of an upward/downward variation is considered. The individual uncertainties are treated as fully uncorrelated and are added in quadrature.
47
5. Measurement of the Muon Reconstruction Efficiency
EtaPhiMap
0 2 4 6 8 10
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
SF
0.9 1 1.1
(a) Staco efficiency in different detector regions
EtaPhiMap
0 2 4 6 8 10
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
SF
0.9 1 1.1
(b) Muid efficiency in different detector regions
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
SF
0.960.981.021.041
(c) Staco efficiency as a function ofpT(µ)
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
SF
0.960.981 1.021.04
(d) Muid efficiency as a function ofpT(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
SF
0.950.91 1.051.1
(e) Staco efficiency as a function ofη(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC Data Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
SF
0.950.91 1.051.1
(f) Muid efficiency as a function ofη(µ)
Figure 5.2.: Reconstruction efficiencies and scale factors for combined muons. The ef-ficiency for the two reconstruction chains Staco (left) and Muid (right), obtained from data (dots) and Monte–Carlo (open triangles) including back-grounds, are shown in the upper part of each figure. The corresponding scale factors (SF) are shown in the lower part.
48
5.5. Systematic uncertainties
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEsCSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
(a) Staco efficiency for the different detector re-gions
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEsCSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
(b) Muid efficiency for the different detector re-gions
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
(c) Staco efficiency as a function ofpT(µ)
[GeV/c]
PT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
(d) Muid efficiency as a function ofpT(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain1
L = 42pb-1
∫
(e) Staco efficiency as a function ofη(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC signal Data, bg corrected Tag & Probe, Data 2010 - Chain2
L = 42pb-1
∫
(f) Muid efficiency as a function ofη(µ)
Figure 5.3.: Background corrected efficiencies for combined muons for the two recon-struction chains Staco (left) and Muid (right), obtained from data (dots) and Monte–Carlo (open triangles).
49
5. Measurement of the Muon Reconstruction Efficiency
Barrel large Barrel small Barrel overlapFeet Transition Endcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
Barrel large Barrel small Barrel overlapFeet Transition Endcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
CB + ST
-1 CB Ldt = 42 pb
∫
Tag and probe, Data 2010, Chain 1
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Ratio
1 1.2
(a) Staco efficiency for the different detector re-gions
Barrel large Barrel small Barrel overlapFeet Transition Endcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
Barrel large Barrel small Barrel overlapFeet Transition Endcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
CB + ST
-1 CB Ldt = 42 pb
∫
Tag and probe, Data 2010, Chain 2
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Ratio
1 1.2
(b) Muid efficiency for the different detector re-gions
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
CB + ST CB Ldt = 42 pb-1
∫
Tag and probe, Data 2010, Chain 1
[GeV]
pT
20 30 40 50 60 70 80 90 100
Ratio
1 1.2
(c) Staco efficiency as a function ofpT(µ)
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
CB + ST CB Ldt = 42 pb-1
∫
Tag and probe, Data 2010, Chain 2
[GeV]
pT
20 30 40 50 60 70 80 90 100
Ratio
1 1.2
(d) Muid efficiency as a function ofpT(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
CB + ST CB Ldt = 42 pb-1
∫
Tag and probe, Data 2010, Chain 1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Ratio
1 1.2
(e) Staco efficiency as a function ofη(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
CB + ST CB Ldt = 42 pb-1
∫
Tag and probe, Data 2010, Chain 2
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Ratio
1 1.2
(f) Muid efficiency as a function ofη(µ)
Figure 5.4.: Efficiencies for combined plus segment-tagged muons (open circles) in com-parison to those for combined muons only (dots) for the two reconstruction chains Staco (left) and Muid (right). The relative gain is shown in the lower part of each figure.
50
5.5. Systematic uncertainties
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 1
Ldt = 42 pb-1
∫
(a) Staco efficiency for the different detector re-gions
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
Barrel largeBarrel smallBarrel overlapFeet TransitionEndcap largeEndcap smallBEEs CSC largeCSC small
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 2
Ldt = 42 pb-1
∫
(b) Muid efficiency for the different detector re-gions
[GeV]
pT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
[GeV]
pT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 1
Ldt = 42 pb-1
∫
(c) Staco efficiency as a function ofpT(µ)
[GeV]
pT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
[GeV]
pT
20 30 40 50 60 70 80 90 100
Efficiency
0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 2
Ldt = 42 pb-1
∫
(d) Muid efficiency as a function ofpT(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 1
Ldt = 42 pb-1
∫
(e) Staco efficiency as a function ofη(µ)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5η
Efficiency
0.7 0.75 0.8 0.85 0.9 0.95 1
MC signal only Data corrected Tag and probe, Data 2010, Chain 2
Ldt = 42 pb-1
∫
(f) Muid efficiency as a function ofη(µ)
Figure 5.5.: Efficiencies for combined plus segment-tagged muons for the two reconstruc-tion chains Staco (left) and Muid (right), obtained from data with back-ground correction (dots) and Monte–Carlo of the signal (open triangles).
51