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| CMS-PAS-SMP-16-012 | ||
| Search for anomalous couplings in semileptonic WW and WZ decays at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| August 2016 | ||
| Abstract: The increased center of mass energy of the LHC Run II allows for a much larger reach to study possible deviations from the standard model in a generic manner, using an effective field theory approach. In this analysis we constrain additional operators that would lead to anomalous WW$\gamma$ or WWZ couplings by studying events with one W boson decaying to an electron or muon and neutrino and one W or Z boson decaying hadronically. The study uses a sample of proton-proton collisions collected with the CMS experiment at a center-of-mass energy of $\sqrt{s}=$ 13 TeV corresponding to an integrated luminosity of 2.3 fb$^{-1}$. Using di-boson mass distributions we derive 95% confidence intervals for the anomalous coupling parameters $\frac{c_{\mathrm{WWW}}}{\Lambda ^2}$ ($ [-9.46 , 9.42]$ TeV$^{-2}$), $\frac{c_\mathrm{W}}{\Lambda ^2}$ ($ [-12.6, 12.0]$ TeV$^{-2}$) and $\frac{c_\mathrm{B}}{\Lambda ^2}$ ($ [-56.1, 55.4]$ TeV$^{-2}$), in agreement with standard model expectations. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1-a:
Comparison between data and simulation of the ${M_\mathrm {pruned}}$ (a,b) and $M_\mathrm{WV}$ (c,d) distributions in the ${\mathrm {t}\overline {\mathrm {t}}}$ control region. The electron channel is shown on (a,c), while the muon channel is shown on (b,d). Details concerning the systematic uncertainties can be found in section 6. |
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Figure 1-b:
Comparison between data and simulation of the ${M_\mathrm {pruned}}$ (a,b) and $M_\mathrm{WV}$ (c,d) distributions in the ${\mathrm {t}\overline {\mathrm {t}}}$ control region. The electron channel is shown on (a,c), while the muon channel is shown on (b,d). Details concerning the systematic uncertainties can be found in section 6. |
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Figure 1-c:
Comparison between data and simulation of the ${M_\mathrm {pruned}}$ (a,b) and $M_\mathrm{WV}$ (c,d) distributions in the ${\mathrm {t}\overline {\mathrm {t}}}$ control region. The electron channel is shown on (a,c), while the muon channel is shown on (b,d). Details concerning the systematic uncertainties can be found in section 6. |
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Figure 1-d:
Comparison between data and simulation of the ${M_\mathrm {pruned}}$ (a,b) and $M_\mathrm{WV}$ (c,d) distributions in the ${\mathrm {t}\overline {\mathrm {t}}}$ control region. The electron channel is shown on (a,c), while the muon channel is shown on (b,d). Details concerning the systematic uncertainties can be found in section 6. |
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Figure 2-a:
Result of the template fit to the ${M_\mathrm {pruned}}$-distributions, electron channel on (a), muon channel on (b). |
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Figure 2-b:
Result of the template fit to the ${M_\mathrm {pruned}}$-distributions, electron channel on (a), muon channel on (b). |
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Figure 3-a:
Comparison of the $M_\mathrm{WV}$ distribution in the data and background estimate for the electron (a,c) and muon channel (b,d) in the WW- (a,b) and WZ-category (c,d). The pink line represents the sum of the backgrounds and a signal with an aTGC value of $c_{\mathrm{WWW}}=$ 12 TeV$^{-2}$. Each figure also shows the difference between data and the SM prediction, divided by the statistical uncertainty of the data-points. |
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Figure 3-b:
Comparison of the $M_\mathrm{WV}$ distribution in the data and background estimate for the electron (a,c) and muon channel (b,d) in the WW- (a,b) and WZ-category (c,d). The pink line represents the sum of the backgrounds and a signal with an aTGC value of $c_{\mathrm{WWW}}=$ 12 TeV$^{-2}$. Each figure also shows the difference between data and the SM prediction, divided by the statistical uncertainty of the data-points. |
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Figure 3-c:
Comparison of the $M_\mathrm{WV}$ distribution in the data and background estimate for the electron (a,c) and muon channel (b,d) in the WW- (a,b) and WZ-category (c,d). The pink line represents the sum of the backgrounds and a signal with an aTGC value of $c_{\mathrm{WWW}}=$ 12 TeV$^{-2}$. Each figure also shows the difference between data and the SM prediction, divided by the statistical uncertainty of the data-points. |
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Figure 3-d:
Comparison of the $M_\mathrm{WV}$ distribution in the data and background estimate for the electron (a,c) and muon channel (b,d) in the WW- (a,b) and WZ-category (c,d). The pink line represents the sum of the backgrounds and a signal with an aTGC value of $c_{\mathrm{WWW}}=$ 12 TeV$^{-2}$. Each figure also shows the difference between data and the SM prediction, divided by the statistical uncertainty of the data-points. |
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Figure 4-a:
Two dimensional limits on the aTGC-parameters. Shown are the expected contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{W}}{\Lambda ^2}$ (a), $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (b) and $\frac {c_\mathrm{W}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (c). The black line shows the region compatible with the observed data at 95% C.L. |
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Figure 4-b:
Two dimensional limits on the aTGC-parameters. Shown are the expected contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{W}}{\Lambda ^2}$ (a), $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (b) and $\frac {c_\mathrm{W}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (c). The black line shows the region compatible with the observed data at 95% C.L. |
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Figure 4-c:
Two dimensional limits on the aTGC-parameters. Shown are the expected contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{W}}{\Lambda ^2}$ (a), $\frac {c_{\mathrm{WWW}}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (b) and $\frac {c_\mathrm{W}}{\Lambda ^2}-\frac {c_\mathrm{B}}{\Lambda ^2}$ (c). The black line shows the region compatible with the observed data at 95% C.L. |
| Tables | |
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Table 1:
Results of the fit to the ${M_\mathrm {pruned}}$ distributions in the range [40, 150] GeV. The pre- and post-fit yields are presented together with their constraints (pre-fit) and resulting total uncertainties (post-fit). The W+jets contribution is allowed to float in the fit, therefore the prefit values do not have any constraint shown. The single top contribution is fixed in the fit. |
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Table 2:
Estimated normalization uncertainties in % for MC derived contributions. Uncertainties smaller than 0.05% for all processes are not listed. |
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Table 3:
Summary of background and signal yields in WW- and WZ-categories. Uncertainties for the single-top, diboson and ${\mathrm {t}\overline {\mathrm {t}}}$ contributions are evaluated as described in section 6, while the uncertainty on W+jets is derived from the statistical uncertainty of the ${M_\mathrm {pruned}}$-fit and the fit with the alternative function. |
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Table 4:
Expected and observed limits at 95% C.L. on single anomalous couplings (other couplings set to zero). |
| Summary |
| While the current limits cannot supersede the results from the LHC Run I [3], it is expected that limits will substantially improve with accumulating luminosity. |
| Additional Figures | |
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Additional Figure 1-a:
The transfer function $\alpha $ used to transport the W+jets background from the sideband to the signal region for the WW-category (a,b) and the WZ-category (c,d) in the electron- (a,c) and muon-channel (b,d). The green shaded bands show the uncertainty on $\alpha $ as obtained from the covariance matrix of the simultaneous fit in the W+jets simulation in the signal and sideband regions. The red and blue lines show the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{SB,MC}$, respectively. The left $y$-axis corresponds to the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{\text{SB,MC}}$, while the right $y$-axis corresponds to the transfer function $\alpha $. |
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Additional Figure 1-b:
The transfer function $\alpha $ used to transport the W+jets background from the sideband to the signal region for the WW-category (a,b) and the WZ-category (c,d) in the electron- (a,c) and muon-channel (b,d). The green shaded bands show the uncertainty on $\alpha $ as obtained from the covariance matrix of the simultaneous fit in the W+jets simulation in the signal and sideband regions. The red and blue lines show the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{SB,MC}$, respectively. The left $y$-axis corresponds to the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{\text{SB,MC}}$, while the right $y$-axis corresponds to the transfer function $\alpha $. |
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Additional Figure 1-c:
The transfer function $\alpha $ used to transport the W+jets background from the sideband to the signal region for the WW-category (a,b) and the WZ-category (c,d) in the electron- (a,c) and muon-channel (b,d). The green shaded bands show the uncertainty on $\alpha $ as obtained from the covariance matrix of the simultaneous fit in the W+jets simulation in the signal and sideband regions. The red and blue lines show the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{SB,MC}$, respectively. The left $y$-axis corresponds to the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{\text{SB,MC}}$, while the right $y$-axis corresponds to the transfer function $\alpha $. |
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Additional Figure 1-d:
The transfer function $\alpha $ used to transport the W+jets background from the sideband to the signal region for the WW-category (a,b) and the WZ-category (c,d) in the electron- (a,c) and muon-channel (b,d). The green shaded bands show the uncertainty on $\alpha $ as obtained from the covariance matrix of the simultaneous fit in the W+jets simulation in the signal and sideband regions. The red and blue lines show the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{SB,MC}$, respectively. The left $y$-axis corresponds to the functions $F_{\mathrm{W}+\text{jets}}^{\text{SR,MC}}$ and $F_{\mathrm{W}+\text{jets}}^{\text{SB,MC}}$, while the right $y$-axis corresponds to the transfer function $\alpha $. |
png pdf |
Additional Figure 2-a:
Two dimensional limits on the aTGC-parameters in the vertex parameterization. Shown are the expeted contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\lambda _{\mathrm{Z}} - \Delta \kappa _{\mathrm{Z}}$ (a), $\lambda _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$(center) and$\Delta \kappa _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$ (b). The black line shows the region compatible with the observed data at 95% C.L. |
png pdf |
Additional Figure 2-b:
Two dimensional limits on the aTGC-parameters in the vertex parameterization. Shown are the expeted contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\lambda _{\mathrm{Z}} - \Delta \kappa _{\mathrm{Z}}$ (a), $\lambda _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$(center) and$\Delta \kappa _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$ (b). The black line shows the region compatible with the observed data at 95% C.L. |
png pdf |
Additional Figure 2-c:
Two dimensional limits on the aTGC-parameters in the vertex parameterization. Shown are the expeted contours for 68% C.L. (blue), 95% C.L. (green) and 99% C.L. (red), for $\lambda _{\mathrm{Z}} - \Delta \kappa _{\mathrm{Z}}$ (a), $\lambda _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$(center) and$\Delta \kappa _{\mathrm{Z}} - \Delta g_1^{\mathrm{Z}}$ (b). The black line shows the region compatible with the observed data at 95% C.L. |
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Compact Muon Solenoid LHC, CERN |
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