8.1. ANN Results
8.1.2. Fit to Data
The result of the fit to data yields a signal strength ofµ = 0.9+1.2−1.1, a normalisation factor kt¯t+bb¯ = 1.27+−0.210.24 for thett¯+ ≥ 1bbackground andktt¯+c¯c = 1.40+−0.620.74 for thett¯+ ≥ 1c. A comparison between the analysis yields and data in each of the fitted regions is available in Fig. 8.2. The fitted NPs are shown in Fig. 8.3.
The observed constraints on the NPs are compatible with the expected ones obtained from the fit to the Asimov dataset. Different pulls of the fitted values of the NPs are visible. The most notable ones are:
• Heavy and light flavour tagging: These pulls result in increased values of the scale factors applied to MC associated toc-tag and mis-tag. The largest component of the c-tagging systematic uncertainty is pulled to -1.03. This is due to the used calibrations for the scale factors, which are based on data from Run 1 which might not be valid for the different tagger choice of Run 2. This is enhanced by the large statistics available for the control regions. The most important component of the light flavour tagging systematic uncertainty is pulled by the regions with large component oftt¯+light jets events.
• tt¯modelling: These pulls are due to the differences on the predictions of the diff er-ent used MC generators, especially the most visible pull on thett¯+c¯cgenerator.
A notable feature of the likelihood fit is that correlations between the NPs are introduced.
Fig. 8.4 shows the correlation coefficients obtained. Even if the uncertainties are taken as uncorrelated before the fit, the correlations are derived by the fit procedure. As expected, the two normalisation factors in the fit for the tt¯+ ≥ 1b and tt¯+ ≥ 1c components of the tt¯+jets background are anti-correlated. An anti-correlation between the tt¯+ ≥ 1b uncertainty and the signal strength uncertainty is found. This correlation is related to the ability of separating signal from background in the signal regions. The correlation becomes larger when using a variable with lower discrimination power.
To study the dependence of the fit result on the different sources of systematic uncertainty, the fit procedure is repeated for each of the considered NPs keeping its value fixed at different values. All the other NPs are allowed to vary in the new fit. Fig. 8.5 shows the variation of the signal strength, defined asimpact on µ, when a considered NPs is fixed at the two values of ˆθ ± σθ, where σθ is the considered pre-fit or post-fit error on the parameter. Only top twenty NPs with the largest impact onµare shown. The sum of the impact onµ of the single systematic uncertainties in quadrature is not the total error on
8.1. ANN Results
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had HT 150 200 250 300 350 400 450 500 550 600 Data / Pred. 0.50.75
50000 ATLAS Internal = 13 TeV, 13.2 fb-1 150 200 250 300 350 400 450 500 550 600 Data / Pred. 0.50.75 150 200250 300350 400450 500550 600650 Data / Pred. 0.50.75
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Figure 8.2.:(a) to (i), post-fit distributions of HThad and ANN in the regions used for the fit to data using the ANN in the signal regions.
8. Results and Limits on t¯tH(H→b ¯b) Production
2
− −1 0 1 2
Electron ID efficiency Electron energy resolution Electron energy scale b-tag Eigenvar. [0]
b-tag Eigenvar. [1]
b-tag Eigenvar. [2]
c-tag Eigenvar. [0]
c-tag Eigenvar. [1]
c-tag Eigenvar. [2]
c-tag Eigenvar. [3]
b-tag extrapolation c-tag extrapolation light-tag Eigenvar. [0]
light-tag Eigenvar. [1]
light-tag Eigenvar. [2]
light-tag Eigenvar. [3]
light-tag Eigenvar. [4]
light-tag Eigenvar. [5]
Jet energy resolution JES BJES JES effective NP 1 JES effective NP 2 JES effective NP 3 JES effective NP 4 JES effective NP 6
intercalibration modelling JES η
intercalibration total stat JES η
JES flavour composition JES flavour response JES pileup offset µ JES pileup offset NPV
-term JES pileup pT
topology JES pileup ρ Jet vertex tagger efficiency Moun energy resolution (ID) Moun energy resolution (MS) Pileup modelling W+HF (Single Lepton, 2b) W+HF (Single Lepton, 3b) 4b) W+HF (Single Lepton, ≥ W+jets norm. (Single Lepton, 4j) W+jets norm. (Single Lepton, 5j)
≥6j) W+jets norm. (Single Lepton, XS WtH PDF
XS WtH QCD Wt diagram subtraction Wt PS & hadronisation Wt radiation Z+jets norm. (Single Lepton) Fakes normalisation (e+jets, 2b) Fakes normalisation (e+jets, 3b)
4b) Fakes norm. (e+jets, ≥
+jets, 2b) Fakes normalisation (µ
+jets, 3b) Fakes normalisation (µ XS other top (t-ch, s-ch, tZ) XS single top (Wt) XS tHjb PDF XS tHjb QCD ttH scale choice (acceptance) ttH PS & hadronisation XS ttH PDF XS tt (inclusive)
1b shower recoil scheme +≥
t t
1b NLO gen. (residual) tt+≥
1b UE modelling +≥
1b MSTW PDF +≥
1b PS & hadronisation (residual) tt+≥
1b Q CMMPS +≥ t t
1b radiation (residual) tt+≥
1b PS & had. (reweighting) tt+≥
1b NLO gen. (reweighting) tt+≥
1b global scale +≥ t t
1b scale choice +≥
t t
1c NLO gen. (residual) tt+≥
1c NLO reweighting tt+≥
1c PS & hadronisation (residual) tt+≥
1c radiation (residual) tt+≥
1c NNLO reweighting pT(t) tt+≥
1c NNLO reweighting pT(tt) tt+≥
tt+light NLO gen. (residual) tt+light PS & hadronisation (residual) tt+light radiation (residual) tt+light NNLO reweighting pT(t) tt+light NNLO reweighting pT(tt) Theory
(b)
Figure 8.3.:Fitted NPs from a fit to the measured data sample using the ANN. (a) NPs associated to instrumental systematic uncertainties; (b) NPs associated to modelling systematic uncertainties.
8.1. ANN Results µdue to the correlations among the systematic uncertainties. The largest impact comes fromtt¯+ ≥1brelated systematic uncertainties.
Fig. 8.6 shows comparisons between data and prediction for the fitted distributions after the fit to data.
19.6 25.5 4.8 0.2 4.3 0.2 8.2 7.0 -5.7 7.1 13.0 1.7 -15.9 -2.8 32.0 -0.9 7.0 12.7 15.0 -13.1 -1.9 -11.7 5.3 -1.4 -4.5 -1.0 100.0
20.4 25.7 -7.8 -25.3 14.0 -4.3 -15.3 -5.5 -18.3 9.2 -10.9 -5.4 -8.3 2.8 -0.1 -2.5 26.9 -1.6 -4.5 -5.0 -6.6 1.9 -25.7 8.0 37.6 100.0 -1.0
-20.0 18.2 -4.9 -4.4 -2.6 13.3 -1.3 -5.5 3.8 8.5 -24.9 0.7 -5.9 11.4 3.2 2.2 -11.9 1.6 1.6 2.9 8.9 -3.6 16.6 -3.2 100.0 37.6 -4.5
18.2 2.1 -4.7 -20.4 8.2 -12.4 -17.8 -0.5 0.3 25.5 -2.1 5.7 -7.8 -8.9 -2.0 -0.0 2.6 -5.2 0.3 10.4 -3.4 20.4 8.4 100.0 -3.2 8.0 -1.4
33.0 31.9 -12.8 -15.5 10.1 -10.9 -9.0 6.1 -5.9 9.0 0.9 -12.2 -8.4 -13.0 -7.7 5.6 20.1 1.7 1.3 -8.7 -3.4 16.4 100.0 8.4 16.6 -25.7 5.3
17.1 -9.0 -0.4 -14.8 8.8 -29.8 -43.7 -0.7 -6.4 16.1 4.6 -14.7 -6.1 -12.3 2.4 -1.3 -6.7 -16.6 -1.0 -16.9 -11.4 100.0 16.4 20.4 -3.6 1.9 -11.7
-15.2 -14.7 2.4 10.8 17.5 -2.5 7.1 -4.6 2.8 3.1 2.4 6.9 5.2 4.3 1.8 0.1 -5.2 -2.6 3.2 -53.0 100.0 -11.4 -3.4 -3.4 8.9 -6.6 -1.9
-15.4 3.8 3.8 10.4 10.6 -10.5 26.4 6.6 -9.4 -6.6 0.6 1.6 -2.2 10.7 1.4 1.5 -6.3 2.1 -0.9 100.0 -53.0 -16.9 -8.7 10.4 2.9 -5.0 -13.1
0.0 10.5 -2.4 2.9 -3.2 6.7 5.3 -2.1 1.0 -7.6 -3.0 -5.3 -4.9 5.6 8.0 1.0 4.9 -40.6 100.0 -0.9 3.2 -1.0 1.3 0.3 1.6 -4.5 15.0
10.2 3.8 -2.8 -10.8 -11.2 -16.4 -19.5 6.8 -0.7 18.2 7.5 2.6 9.4 -7.4 -6.4 -0.7 12.2 100.0 -40.6 2.1 -2.6 -16.6 1.7 -5.2 1.6 -1.6 12.7
21.0 25.6 -13.0 -19.1 3.4 -1.2 -11.4 -9.5 -0.7 2.5 3.3 -13.4 12.0 -2.4 -0.3 2.7 100.0 12.2 4.9 -6.3 -5.2 -6.7 20.1 2.6 -11.9 26.9 7.0
-4.8 5.5 0.1 1.0 -1.6 -1.4 0.6 -5.5 -1.6 -1.3 -4.2 0.0 5.7 9.3 -0.9 100.0 2.7 -0.7 1.0 1.5 0.1 -1.3 5.6 -0.0 2.2 -2.5 -0.9
-18.6 5.4 1.9 5.6 17.2 13.4 3.0 -8.1 5.9 13.3 10.3 1.4 2.5 2.1 100.0 -0.9 -0.3 -6.4 8.0 1.4 1.8 2.4 -7.7 -2.0 3.2 -0.1 32.0
-32.1 38.3 21.2 27.9 -7.2 -4.6 16.2 -4.2 -6.8 -14.2 -11.0 28.3 30.2 100.0 2.1 9.3 -2.4 -7.4 5.6 10.7 4.3 -12.3 -13.0 -8.9 11.4 2.8 -2.8 -11.9 -5.4 -2.3 2.3 -11.1 10.3 -27.2 -11.3 -16.7 2.3 11.8 -7.9 100.0 30.2 2.5 5.7 12.0 9.4 -4.9 -2.2 5.2 -6.1 -8.4 -7.8 -5.9 -8.3 -15.9
-0.8 18.1 34.3 0.7 5.2 4.9 0.0 -8.4 -8.6 9.9 17.5 100.0 -7.9 28.3 1.4 0.0 -13.4 2.6 -5.3 1.6 6.9 -14.7 -12.2 5.7 0.7 -5.4 1.7
11.8 -12.5 32.7 -7.9 14.3 -2.0 -6.2 -7.4 -9.4 -1.3 100.0 17.5 11.8 -11.0 10.3 -4.2 3.3 7.5 -3.0 0.6 2.4 4.6 0.9 -2.1 -24.9 -10.9 13.0
6.4 7.9 -4.9 -13.3 21.0 -30.6 -37.6 8.0 3.1 100.0 -1.3 9.9 2.3 -14.2 13.3 -1.3 2.5 18.2 -7.6 -6.6 3.1 16.1 9.0 25.5 8.5 9.2 7.1
-14.8 -33.9 0.6 -4.5 -9.3 10.8 6.0 -4.0 100.0 3.1 -9.4 -8.6 -16.7 -6.8 5.9 -1.6 -0.7 -0.7 1.0 -9.4 2.8 -6.4 -5.9 0.3 3.8 -18.3 -5.7
44.2 1.7 -9.4 6.5 0.9 -1.0 22.8 100.0 -4.0 8.0 -7.4 -8.4 -11.3 -4.2 -8.1 -5.5 -9.5 6.8 -2.1 6.6 -4.6 -0.7 6.1 -0.5 -5.5 -5.5 7.0
-7.2 -15.0 13.5 57.4 36.8 0.7 100.0 22.8 6.0 -37.6 -6.2 0.0 -27.2 16.2 3.0 0.6 -11.4 -19.5 5.3 26.4 7.1 -43.7 -9.0 -17.8 -1.3 -15.3 8.2 -19.4 15.1 -13.6 -11.9 -56.1 100.0 0.7 -1.0 10.8 -30.6 -2.0 4.9 10.3 -4.6 13.4 -1.4 -1.2 -16.4 6.7 -10.5 -2.5 -29.8 -10.9 -12.4 13.3 -4.3 0.2
23.4 -27.2 15.1 21.5 100.0 -56.1 36.8 0.9 -9.3 21.0 14.3 5.2 -11.1 -7.2 17.2 -1.6 3.4 -11.2 -3.2 10.6 17.5 8.8 10.1 8.2 -2.6 14.0 4.3
-30.9 -2.9 5.8 100.0 21.5 -11.9 57.4 6.5 -4.5 -13.3 -7.9 0.7 2.3 27.9 5.6 1.0 -19.1 -10.8 2.9 10.4 10.8 -14.8 -15.5 -20.4 -4.4 -25.3 0.2
0.4 -27.9 100.0 5.8 15.1 -13.6 13.5 -9.4 0.6 -4.9 32.7 34.3 -2.3 21.2 1.9 0.1 -13.0 -2.8 -2.4 3.8 2.4 -0.4 -12.8 -4.7 -4.9 -7.8 4.8
-0.4 100.0 -27.9 -2.9 -27.2 15.1 -15.0 1.7 -33.9 7.9 -12.5 18.1 -5.4 38.3 5.4 5.5 25.6 3.8 10.5 3.8 -14.7 -9.0 31.9 2.1 18.2 25.7 25.5 100.0 -0.4 0.4 -30.9 23.4 -19.4 -7.2 44.2 -14.8 6.4 11.8 -0.8 -11.9 -32.1 -18.6 -4.8 21.0 10.2 0.0 -15.4 -15.2 17.1 33.0 18.2 -20.0 20.4 19.6
1c)≥k(tt+ 1b)≥k(tt+ Httµ tt+light NNLO reweighting pT(tt) tt+light radiation (residual) tt+light PS & had. (residual) tt+light generator (residual) 1c radiation (residual)≥tt+ 1c NLO reweighting≥tt+ 1c generator (residual)≥tt+ 1b generator (reweighting)≥tt+ 1b radiation (residual)≥tt+ 1b PS & had. (residual)≥tt+ 1b generator (residual)≥tt+ XS tt (inclusive) 4b)≥Fakes norm. (e+jets, Fakes normalisation (e+jets, 3b) Fakes normalisation (e+jets, 2b) W+HF (Single Lepton, 2b) JES flavour composition JES effective NP 1 Jet energy resolution light-tag Eigenvar. [0] b-tag extrapolation c-tag Eigenvar. [1] c-tag Eigenvar. [0] b-tag Eigenvar. [0]
b-tag Eigenvar. [0]
c-tag Eigenvar. [0]
c-tag Eigenvar. [1]
b-tag extrapolation light-tag Eigenvar. [0]
Jet energy resolution JES effective NP 1 JES flavour composition W+HF (Single Lepton, 2b) Fakes normalisation (e+jets, 2b) Fakes normalisation (e+jets, 3b) 4b) Fakes norm. (e+jets, ≥
XS tt (inclusive) 1b generator (residual) tt+≥
1b PS & had. (residual) tt+≥
1b radiation (residual) tt+≥
1b generator (reweighting) tt+≥
1c generator (residual) tt+≥
1c NLO reweighting tt+≥
1c radiation (residual) tt+≥
tt+light generator (residual) tt+light PS & had. (residual) tt+light radiation (residual) tt+light NNLO reweighting pT(tt) H t t µ 1b) k(tt+≥
1c) k(tt+≥
Figure 8.4.:The correlation matrix for the NPs obtained from the fit to data in the sin-gle lepton channel under the signal-plus-background hypothesis. Only NPs with a correlation coefficient of at least 30% with any other parameter are displayed.
8. Results and Limits on t¯tH(H→b ¯b) Production Fakes normalisation (e+jets, 3b)
tt+light NNLO reweighting pT(t) c-tag Eigenvar. [1]
XS ttH QCD 1b global scale
≥ + t t
ttH PS & hadronisation 1b scale choice
≥ + t t
b-tag Eigenvar. [1]
light-tag Eigenvar. [0]
1b shower recoil scheme +≥
t t
Jet vertex tagger efficiency 1c radiation (residual)
≥ tt+
tt+light NLO gen. (residual) tt+light PS & had. (residual) 1b PS & had. (reweighting) tt+≥
tt+light radiation (residual) 1b NLO gen. (residual) tt+≥
1b)
≥ k(tt+
1b NLO gen. (reweighting) tt+≥
1b radiation (residual)
≥
Pre-fit impact on θ
=+∆
θ0 θ0=-∆θ µ: Post-fit impact on
θ
=+∆
θ0 θ0=-∆θ Nuis. Param. Pull
ATLAS Internal = 13 TeV, 13.2 fb-1
s
Figure 8.5.:Ranking of the NPs used in the fit according to their effect on the best fitted µfor the single lepton channel ANN fit to data. The top twenty parameters are shown. The empty blue rectangles correspond to the pre-fit impact while the filled blue ones to post-fit impact. The k is the normalisation factor (with respect to prediction) for thett¯+≥ 1bcomponent.
4j,2b 4j,3b 4j,4b 5j,2b 5j,3b 5j,≥4b ≥6j,2b ≥6j,3b ≥6j,≥4b
107 ATLAS Internal = 13 TeV, 13.2 fb-1
Figure 8.6.:Yield comparison between data and prediction after the fit to the measured data sample using the ANN.