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| CMS-PAS-SMP-14-011 | ||
| A search for electroweak-induced production of $\mathrm{W} \gamma$ with two jets and constraints on anomalous quartic gauge couplings in pp collisions at $ \sqrt{s} =$ 8 TeV | ||
| CMS Collaboration | ||
| January 2016 | ||
| Abstract: A search for electroweak-induced production of $ \mathrm{W} \gamma $ with two jets in W leptonic decay mode in pp collisions at $\sqrt{s} =$ 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.7 fb$^{-1}$ collected by the CMS detector. Candidate events are selected with exactly one muon or electron, missing transverse energy, one photon, and two jets with large rapidity separation. The electroweak contribution is observed with significance of the excess 2.7$\sigma$, the cross section in the fiducial region is measured to be 10.8 $\pm$ 4.1 (stat) $\pm$ 3.4 (syst) $\pm$ 0.3 (lumi) fb, which is consistent with the Standard Model prediction. The upper limit on the electroweak signal strength is 4.3 at 95% confidence level. When only the non-$ \mathrm{W} \gamma $ plus two jets contribution is considered as background, the cross section in the same region is measured to be 23.2 $\pm$ 4.3 (stat) $\pm$ 1.7 (syst) $\pm$ 0.6 (lumi) fb, which is consistent with the Standard Model electroweak+QCD prediction. Experimental limits on dimension eight anomalous quartic gauge couplings $f_{M,0-7}/\Lambda^4$, $f_{T,0-2}/\Lambda^4$, and $f_{T,5-7}/\Lambda^4$ are set at 95% confidence level. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 06 (2017) 106. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1-a:
Representative Feynman diagrams for the EWK $ \mathrm{W \gamma jj }$ production at the LHC: (a) Bremsstrahlung, (b) Bremsstrahlung with TGC, and (c) VBS with quartic gauge coupling. |
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Figure 1-b:
Representative Feynman diagrams for the EWK $ \mathrm{W \gamma jj }$ production at the LHC: (a) Bremsstrahlung, (b) Bremsstrahlung with TGC, and (c) VBS with quartic gauge coupling. |
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Figure 1-c:
Representative Feynman diagrams for the EWK $ \mathrm{W \gamma jj }$ production at the LHC: (a) Bremsstrahlung, (b) Bremsstrahlung with TGC, and (c) VBS with quartic gauge coupling. |
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Figure 2-a:
The signal region $M_{ \mathrm{jj} } $ distribution, for muon channel (a) and electron channel (b). The backgrounds for misidentified photons and electrons are estimated from data as described in the text. The dibosons contribution include $ \mathrm{ WV(+\gamma ) } $ and $ \mathrm{ Z\gamma (+jets) } $ processes. The top contribution includes both the $\mathrm{ t \bar{t} }\gamma $ and single top quark processes. Signal contribution is shown on top of backgrounds. The last bin has been extended to include the overflow events, and the hatched error bands include the full statistical and systematic uncertainties on the backgrounds summed in quadrature. The uncertainty in the ratio plot corresponds to this hatched error. |
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Figure 2-b:
The signal region $M_{ \mathrm{jj} } $ distribution, for muon channel (a) and electron channel (b). The backgrounds for misidentified photons and electrons are estimated from data as described in the text. The dibosons contribution include $ \mathrm{ WV(+\gamma ) } $ and $ \mathrm{ Z\gamma (+jets) } $ processes. The top contribution includes both the $\mathrm{ t \bar{t} }\gamma $ and single top quark processes. Signal contribution is shown on top of backgrounds. The last bin has been extended to include the overflow events, and the hatched error bands include the full statistical and systematic uncertainties on the backgrounds summed in quadrature. The uncertainty in the ratio plot corresponds to this hatched error. |
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Figure 3:
Comparison of predicted and observed $p_{\mathrm {T}}^{\mathrm {W}}$ distributions with electron and muon combined channels. The last $p_{\mathrm {T}}^{\mathrm {W}}$ bin has been extended to include overflow contribution. The dash red line depicts a representative signal distribution with anomalous coupling parameter $f_{M,0}/\Lambda ^{4}= $ 44 TeV$^{-4}$. The bands represent the statistical and systematic uncertainties on signal and background predictions squared. The data are shown with statistical uncertainties only. |
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Figure 4-a:
Comparison of the limits on the dimension 8 AQGC parameters obtained from this study, together with results from $ \mathrm{ WV } \gamma $ production [13], same sign WW production [74], VBS $ \mathrm{Z} \gamma $ production [26], exclusive $\gamma \gamma \to \mathrm{WW} $ production at CMS [17,72] and W$\gamma \gamma $ production at ATLAS [73]. |
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Figure 4-b:
Comparison of the limits on the dimension 8 AQGC parameters obtained from this study, together with results from $ \mathrm{ WV } \gamma $ production [13], same sign WW production [74], VBS $ \mathrm{Z} \gamma $ production [26], exclusive $\gamma \gamma \to \mathrm{WW} $ production at CMS [17,72] and W$\gamma \gamma $ production at ATLAS [73]. |
| Tables | |
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Table 1:
Summary of the base line selection criteria. |
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Table 2:
Number of events per process, with combined statistical and systematic uncertainty. The ``Total prediction'' represents the sum of all the individual contributions. The multijets with one jet misidentified as an electron background is negligible in this region. |
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Table 3:
Summary of the measured and predicted observables. |
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Table 4:
Observed and expected shape-based exclusion limits for each AQGC parameter at 95% CL, no form factor is applied. |
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Compact Muon Solenoid LHC, CERN |
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