CMS-PAS-B2G-16-007 | ||

Combination of searches for WW, WZ, ZZ, WH, and ZH resonances at $\sqrt{s} = $ 8 and 13 TeV | ||

CMS Collaboration | ||

May 2016 | ||

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Abstract:
The statistical combination of searches for massive resonances decaying to pairs of W, Z, and Higgs bosons based on pp collision data collected by the CMS experiment at the CERN LHC is presented. The data are taken at a centre-of-mass energy of 8 and 13 TeV and correspond to an integrated luminosity of 19.7 fb$^{-1}$ and 2.6 fb$^{-1}$ respectively. The results are interpreted in the context of a heavy vector triplet model that mimics the properties of composite Higgs models predicting a W' and a Z' decaying to WZ, WH, WW, and ZH and a model with a "bulk" graviton that decays into WW and ZZ. Combined cross section limits as a function of resonance mass are obtained. The combined significance of potential resonances of 1.8-2 TeV are evaluated in each signal hypothesis.
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Links:
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These preliminary results are superseded in this paper, PLB 774 (2017) 533.The superseded preliminary plots can be found here. |

Figures | |

png pdf |
Figure 1-a:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{WZ/WH})$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{ WZ/WH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 1-b:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{WZ/WH})$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{ WZ/WH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 1-c:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{WZ/WH})$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm W^\prime } \to \mathrm{ WZ/WH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 2:
Comparison of the observed (solid) and expected (dashed) exclusion limits at 95% CL obtained by combining only 8 TeV or only 13 TeV searches to the results from the combination of all the 8 and 13 TeV results. |

png pdf |
Figure 3-a:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 3-b:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 3-c:
(top left) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (top right) Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm Z^\prime } \to \mathrm{ WW/ZH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. (bottom) Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In each of the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 4:
Comparison of the observed (solid) and expected (dashed) exclusion limits at 95% CL obtained by combining only 8 TeV or only 13 TeV searches to the results from the combination of all the 8 and 13 TeV results. |

png pdf |
Figure 5-a:
Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm V^\prime } \to \mathrm{ WV/VH }$ ($ {\rm V^\prime } = {\rm W^\prime } $, ${\rm Z^\prime }$ and $\mathrm{ V=W,Z }$) as a function of the resonance mass obtained by combining the 8 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. |

png pdf |
Figure 5-b:
Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to {\rm V^\prime } \to \mathrm{ WV/VH })$ as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by the HVT model B is overlaid. |

png pdf |
Figure 5-c:
Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In all the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 6:
Comparison of the observed (solid) and expected (dashed) exclusion limits at 95% CL obtained by combining only 8 TeV or only 13 TeV searches to the results from the combination of all the 8 and 13 TeV results. |

png pdf |
Figure 7:
Exclusion regions in the plane of the HVT-model couplings ($g_{\rm V}c_{\rm H}$, $g^2c_{\rm F}/g_{\rm V}$ ) for three resonance masses, 1.5, 2, and 3 TeV, where $g$ denotes the weak gauge coupling. The point B of the benchmark model used in the analysis is also shown. The boundaries of the regions outside these lines are excluded by this search are indicated by the solid and dashed lines. The areas indicated by the solid shading correspond to regions where the resonance width is predicted to be more than 7% of the resonance mass and the narrow-resonance assumption is not satisfied. |

png pdf |
Figure 8-a:
Observed (black solid) and expected (black dashed) exclusion limits at 95% CL on $\sigma ( \rm pp \to G_{bulk} \to \mathrm{ VV })$ ($\mathrm{ V=W,Z}$) as a function of the resonance mass obtained by combining the 13 TeV diboson searches. The curve corresponding to the cross sections predicted by bulk graviton model is overlaid. |

png pdf |
Figure 8-b:
Exclusion limits at 95% CL on the signal strength as a function of the resonance mass obtained by combining the 8 and 13 TeV diboson searches. In all the three plots the different colored lines correspond to the searches entering the combination. |

png pdf |
Figure 9:
Comparison of the observed (solid) and expected (dashed) exclusion limits at 95% CL obtained by combining only 8 TeV or only 13 TeV searches to the results from the combination of all the 8 and 13 TeV results. |

Tables | |

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Table 1:
Summary of the properties of heavy resonances considered in the combination. |

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Table 2:
Summary of the signal efficiencies of all analysis channels for all signal models for a 2 TeV resonance in both high-purity (HP) and low-purity (LP) categories. The signal efficiencies are in percent and include the branching ratios of the two vector bosons to the final state of the analysis channel, effects from detector acceptance, as well as reconstruction and selection efficiencies. |

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Table 3:
Summary of the dominant backgrounds and their estimation methods in each analysis channel. |

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Table 4:
Correlation of systematic uncertainties. |

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Table 5:
Statistical significance of excesses observed at 1.8 TeV in the various searches, expressed in standard deviations. |

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Table 6:
Statistical significance of excesses observed at 1.9 TeV in the various searches, expressed in standard deviations. |

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Table 7:
Statistical significance of excesses observed at 2 TeV in the various searches, expressed in standard deviations. |

Summary |

The statistical combination of searches for massive resonances decaying to WW, ZZ, WZ, WH, and ZH boson pairs has been presented. The considered searches are based on pp collision data collected by the CMS experiment at a centre-of-mass energy of 8 and 13 TeV, corresponding to an integrated luminosity of 19.7 fb$^{-1}$ and 2.2-2.6 fb$^{-1}$, respectively. The results are interpreted in the context of heavy vector singlet and triplet models predicting a W' and a Z' decaying to WZ, WH, WW, and ZH and a model with a "bulk" graviton that decays into WW and ZZ. The combination yields the most stringent resonance mass limits to date on W' and Z' singlets at 2.3 TeV and 1.8 TeV, respectively, and on a heavy vector triplet at 2.4 TeV. The combination also yields the most stringent cross section limits on a narrow bulk graviton resonance to date in the mass range from 0.8 to 4 TeV. Finally, the combined significance of a potential resonances at 1.8-2.0 TeV is evaluated and found to be 0.9$\sigma$ for the hypothesis of a W' that yields the highest significance among all considered signal hypotheses. |

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Compact Muon Solenoid LHC, CERN |