CMSPASFTR18036  
Anomalous couplings in the ttZ final state at the HLLHC  
CMS Collaboration  
December 2018  
Abstract: The electroweak couplings of the top quark provide a crucial window to physics beyond the standard model and can be put to stringent tests with the CERN HighLuminosity LHC (HLLHC). The expected sensitivity of the CMS detector for anomalous electroweak top quark interactions based on differential cross section measurements of the ttZ process in the three lepton final state is provided for a HLLHC scenario with 3000 fb$^{1}$ of protonproton collision data at a centreofmass energy of 14 TeV.  
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; 
Figures & Tables  Summary  Additional Figures & Tables  References  CMS Publications 

Figures  
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Figure 1:
Representative Feynman diagram for the ttZ process. 
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Figure 2:
Differential cross sections with respect to $ { {p_\textrm {T}} ({\mathrm {Z}})} $ (left) and $\cos\theta ^\ast _{{\mathrm {Z}}}$ (right) in the ttZ (${N_{\textrm {lep}}}= $ 3) channel as specified in Table 2 and for the Phase2 scenario. For $\cos\theta ^\ast _{{\mathrm {Z}}}$, an additional requirement of $ { {p_\textrm {T}} ({\mathrm {Z}})} > $ 200 GeV is applied. The SM distributions are shown in black with systematic uncertainties, while colored lines show hypotheses for ${C_\text {tZ}} $=2 ($\Lambda $/TeV)$^2$ and ${C_\text {tZ}^\text {[Im]}} = $ 2 ($\Lambda $/TeV)$^2$, with yields that are areanormalized to the SM distribution. The noninformative contribution to ttZ is described in Sec. 4 and shown hatched. Backgrounds are shown in solid colors. 
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Figure 2a:
Differential cross sections with respect to $ { {p_\textrm {T}} ({\mathrm {Z}})} $ in the ttZ (${N_{\textrm {lep}}}= $ 3) channel as specified in Table 2 and for the Phase2 scenario. For $\cos\theta ^\ast _{{\mathrm {Z}}}$, an additional requirement of $ { {p_\textrm {T}} ({\mathrm {Z}})} > $ 200 GeV is applied. The SM distributions are shown in black with systematic uncertainties, while colored lines show hypotheses for ${C_\text {tZ}} $=2 ($\Lambda $/TeV)$^2$ and ${C_\text {tZ}^\text {[Im]}} = $ 2 ($\Lambda $/TeV)$^2$, with yields that are areanormalized to the SM distribution. The noninformative contribution to ttZ is described in Sec. 4 and shown hatched. Backgrounds are shown in solid colors. 
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Figure 2b:
Differential cross sections with respect to $\cos\theta ^\ast _{{\mathrm {Z}}}$ in the ttZ (${N_{\textrm {lep}}}= $ 3) channel as specified in Table 2 and for the Phase2 scenario. For $\cos\theta ^\ast _{{\mathrm {Z}}}$, an additional requirement of $ { {p_\textrm {T}} ({\mathrm {Z}})} > $ 200 GeV is applied. The SM distributions are shown in black with systematic uncertainties, while colored lines show hypotheses for ${C_\text {tZ}} $=2 ($\Lambda $/TeV)$^2$ and ${C_\text {tZ}^\text {[Im]}} = $ 2 ($\Lambda $/TeV)$^2$, with yields that are areanormalized to the SM distribution. The noninformative contribution to ttZ is described in Sec. 4 and shown hatched. Backgrounds are shown in solid colors. 
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Figure 3:
Signal region yields from simulation for SM processes (colored histograms). The yields are estimated for an integrated luminosity of 3/ab, the cross section is scaled to 14 TeV. The total SM yield is shown with the black line, the dashed red line reflects the total expected yield assuming modified couplings, with the chosen value ${C_\text {tZ}} = $ 2 ($\Lambda $/TeV)$^2$. The hatched area represents the noninformative contribution to ttZ as described in Sec. 4. 
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Figure 4:
Individual likelihood ratio for the Wilson coefficients $ {C_{\phi t}} $ and ${C_{\phi Q}^{}}$ (top) and ${C_\text {tZ}}$ and ${C_\text {tZ}^\text {[Im]}}$ (bottom) for the ttZ process. Here, only one Wilson coefficient at a time is considered nonzero. The 68% (95%) CL intervals are given in green (red). 
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Figure 4a:
Individual likelihood ratio for the Wilson coefficients $ {C_{\phi t}} $ for the ttZ process. Other Wilson coefficients are set to zero. The 68% (95%) CL interval is given in green (red). 
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Figure 4b:
Individual likelihood ratio for the Wilson coefficients ${C_{\phi Q}^{}}$ for the ttZ process. Other Wilson coefficients are set to zero. The 68% (95%) CL interval is given in green (red). 
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Figure 4c:
Individual likelihood ratio for the Wilson coefficients ${C_\text {tZ}}$ for the ttZ process. Other Wilson coefficients are set to zero. The 68% (95%) CL interval is given in green (red). 
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Figure 4d:
Individual likelihood ratio for the Wilson coefficients ${C_\text {tZ}^\text {[Im]}}$ for the ttZ process. Other Wilson coefficients are set to zero. The 68% (95%) CL interval is given in green (red). 
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Figure 5:
Individual profiled likelihood ratio for the Wilson coefficients $ {C_{\phi t}} $ and ${C_{\phi Q}^{}}$ (top) and ${C_\text {tZ}}$ and ${C_\text {tZ}^\text {[Im]}}$ (bottom) for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). 
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Figure 5a:
Individual profiled likelihood ratio for the Wilson coefficients $ {C_{\phi t}} $ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). 
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Figure 5b:
Individual profiled likelihood ratio for the Wilson coefficients ${C_{\phi Q}^{}}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). 
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Figure 5c:
Individual profiled likelihood ratio for the Wilson coefficients ${C_\text {tZ}}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). 
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Figure 5d:
Individual profiled likelihood ratio for the Wilson coefficients ${C_\text {tZ}^\text {[Im]}}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). 
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Figure 6:
Scan of the negative likelihood in the ${C_{\phi Q}^{}} / {C_{\phi t}}$ (left) and ${C_\text {tZ}} / {C_\text {tZ}^\text {[Im]}}$ parameter planes (right) for the ttZ process under the SM hypothesis. The 68% (95%) CL contour lines are given in green (red). 
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Figure 6a:
Scan of the negative likelihood in the ${C_{\phi Q}^{}} / {C_{\phi t}}$ parameter plane for the ttZ process under the SM hypothesis. The 68% (95%) CL contour lines are given in green (red). 
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Figure 6b:
Scan of the negative likelihood in the ${C_\text {tZ}} / {C_\text {tZ}^\text {[Im]}}$ parameter plane for the ttZ process under the SM hypothesis. The 68% (95%) CL contour lines are given in green (red). 
Tables  
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Table 1:
Simulated processes with a MonteCarlo sample size of one million events, the cross section for $\sqrt {s}=13 TeV $ and the scale factor for $\sqrt {s}=$ 14 TeV . Here, $\ell =$ e, $\mu$, $\tau $ and $\nu _\ell =\nu _e$, $\nu _\mu$, $\nu _\tau $. 
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Table 2:
Event selection and object level thresholds for the ttZ selection. 
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Table 3:
Definition of the ttZ signal regions. 
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Table 4:
The sources of systematic uncertainty grouped in experimental systematic uncertainties (exp.) and theoretical uncertainties (theo.) as well as their impacts on reconstructed objects and event yields. 
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Table 5:
Expected 68% and 95% CL intervals, where one Wilson coefficient at a time is considered nonzero. 
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Table 6:
Expected 68% and 95% CL intervals for the selected Wilson coefficients in a profiled scan over the 2D parameter planes ${C_{\phi Q}^{}} / {C_{\phi t}}$ and ${C_\text {tZ}} / {C_\text {tZ}^\text {[Im]}}$. The respective second parameter of the scan is left free. 
Summary 
The CMS sensitivity to anomalous interactions using ttZ measurements in the HLLHC era corresponding to a simulated data set of 3 ab$^{1}$ of integrated luminosity has been been estimated in the context of SMEFT. The considered scenario assumed advances in both experimental methods and theoretical descriptions of the relevant physics effects. With the reduced theoretical and experimental uncertainties, tight constraints are expected in two planes spanned by a total of four Wilson coefficients and in one dimensional loglikelihood scans. 
Additional Figures  
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Additional Figure 1:
Scan of the negative likelihood in the $C_\text {1V}$/$C_\text {1A}$ parameter plane for the ttZ process under the SM hypothesis. The 68% (95%) CL contour lines are given in green (red). Parameter definition according to [41,45]. The Standard Model values for $C_\text {1V}$ and $C_\text {1A}$ correspond to 0.244 and 0.601 respectively. 
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Additional Figure 2:
Scan of the negative likelihood in the $C_\text {2V}$/$C_\text {2A}$ parameter plane for the ttZ process under the SM hypothesis. The 68% (95%) CL contour lines are given in green (red). Parameter definition according to [41,45]. 
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Additional Figure 3:
Profiled likelihood ratio for the Wilson coefficient $C_\text {1V}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). Parameter definition according to [41,45]. The Standard Model value for $C_\text {1V}$ corresponds to 0.244. 
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Additional Figure 4:
Profiled likelihood ratio for the Wilson coefficient $C_\text {1A}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). Parameter definition according to [41,45]. The Standard Model value for $C_\text {1A}$ corresponds to 0.601. 
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Additional Figure 5:
Profiled likelihood ratio for the Wilson coefficient $C_\text {2V}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). Parameter definition according to [41,45]. 
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Additional Figure 6:
Profiled likelihood ratio for the Wilson coefficient $C_\text {2A}$ for the ttZ process under the SM hypothesis. The 68% (95%) CL intervals are given in green (red). Parameter definition according to [41,45]. 
Additional Tables  
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Additional Table 1:
Expected 68 % and 95 % CL intervals for the selected anomalous coupling parameters in a profiled scan over the 2D parameter planes $C_\text {1V}$/$C_\text {1A}$ and $C_\text {2V}$/$C_\text {2A}$. The respective second parameter of the scan is left free. Parameter definition according to [41,45]. The Standard Model values for $C_\text {1V}$ and $C_\text {1A}$ correspond to 0.244 and 0.601 respectively. 
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Additional Table 2:
Expected 68 % and 95 % CL intervals for the selected anomalous coupling parameters in a profiled scan over the 2D parameter planes $\delta X_{t t}^{L}$/$\delta X_{t t}^{R}$ and $\delta d_{V}^{Z}$/$\delta d_{A}^{Z}$. The respective second parameter of the scan is left free. Parameter definition according to [45]. 
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Additional Table 3:
Expected 68 % and 95 % CL intervals, where one anomalous coupling parameter at a time is considered nonzero. Parameter definition according to [45]. 
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