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| CMS-EXO-21-015 ; CERN-EP-2024-326 | ||
| Search for a neutral gauge boson with nonuniversal fermion couplings in vector boson fusion processes in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 26 December 2024 | ||
| Submitted to Phys. Rev. Lett. | ||
| Abstract: The first search for a heavy neutral spin-1 gauge boson (Z') with nonuniversal fermion couplings produced via vector boson fusion processes and decaying to tau leptons or W bosons is presented. The analysis is performed using LHC data at $ \sqrt{s} = $ 13 TeV, collected from 2016 to 2018 and corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The data are consistent with the standard model predictions. Upper limits are set on the product of the cross section for production of the Z' boson and its branching fraction to $ \tau\tau $ or WW. The presence of a Z' boson decaying to $ \tau^{+}\tau^{-} $ (W$^{+}$W$^{-}$) is excluded for masses up to 2.45 (1.60) TeV, depending on the Z' boson coupling to SM weak bosons, and assuming a $ {\mathrm{Z}^{'}} \to\tau^{+}\tau^{-} $ (W$^{+}$W$^{-}$) branching fraction of 50%. | ||
| Links: e-print arXiv:2412.19261 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Observed $ m(\ell_{1},\ell_{2},p_{\mathrm{T}}^\text{miss}) $ for the data, and the post-fit backgrounds (stacked histograms), in the signal region for the $ \mu\tau_\mathrm{h} $ (upper left), $ \mathrm{e}\tau_\mathrm{h} $ (upper right), $ \tau_\mathrm{h}\tau_\mathrm{h} $ (lower left), and $ \mathrm{e}\mu $ (lower right) channels. The lower panels show ratios of the data to the pre-fit background prediction and post-fit background yields as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit uncertainty. The dashed lines correspond to the signal expectation for Z' boson masses of 1 TeV (black) and 2.5 TeV (magenta) decaying to $ \tau^{+}\tau^{-} $, normalized to cross sections of 199.4 fb and 0.7504 fb respectively. The dashed brown line corresponds to a Z' boson mass of 1.25 TeV decaying to W$^{+}$W$^{-}$, normalized to a cross section of 61.14 fb. The signal cross sections correspond to $ \{\kappa_{\mathrm{V}},g_{3},g_{1,\,2} \} = \{ 1,1,0\} $. |
png pdf |
Figure 1-a:
Observed $ m(\ell_{1},\ell_{2},p_{\mathrm{T}}^\text{miss}) $ for the data, and the post-fit backgrounds (stacked histograms), in the signal region for the $ \mu\tau_\mathrm{h} $ (upper left), $ \mathrm{e}\tau_\mathrm{h} $ (upper right), $ \tau_\mathrm{h}\tau_\mathrm{h} $ (lower left), and $ \mathrm{e}\mu $ (lower right) channels. The lower panels show ratios of the data to the pre-fit background prediction and post-fit background yields as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit uncertainty. The dashed lines correspond to the signal expectation for Z' boson masses of 1 TeV (black) and 2.5 TeV (magenta) decaying to $ \tau^{+}\tau^{-} $, normalized to cross sections of 199.4 fb and 0.7504 fb respectively. The dashed brown line corresponds to a Z' boson mass of 1.25 TeV decaying to W$^{+}$W$^{-}$, normalized to a cross section of 61.14 fb. The signal cross sections correspond to $ \{\kappa_{\mathrm{V}},g_{3},g_{1,\,2} \} = \{ 1,1,0\} $. |
png pdf |
Figure 1-b:
Observed $ m(\ell_{1},\ell_{2},p_{\mathrm{T}}^\text{miss}) $ for the data, and the post-fit backgrounds (stacked histograms), in the signal region for the $ \mu\tau_\mathrm{h} $ (upper left), $ \mathrm{e}\tau_\mathrm{h} $ (upper right), $ \tau_\mathrm{h}\tau_\mathrm{h} $ (lower left), and $ \mathrm{e}\mu $ (lower right) channels. The lower panels show ratios of the data to the pre-fit background prediction and post-fit background yields as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit uncertainty. The dashed lines correspond to the signal expectation for Z' boson masses of 1 TeV (black) and 2.5 TeV (magenta) decaying to $ \tau^{+}\tau^{-} $, normalized to cross sections of 199.4 fb and 0.7504 fb respectively. The dashed brown line corresponds to a Z' boson mass of 1.25 TeV decaying to W$^{+}$W$^{-}$, normalized to a cross section of 61.14 fb. The signal cross sections correspond to $ \{\kappa_{\mathrm{V}},g_{3},g_{1,\,2} \} = \{ 1,1,0\} $. |
png pdf |
Figure 1-c:
Observed $ m(\ell_{1},\ell_{2},p_{\mathrm{T}}^\text{miss}) $ for the data, and the post-fit backgrounds (stacked histograms), in the signal region for the $ \mu\tau_\mathrm{h} $ (upper left), $ \mathrm{e}\tau_\mathrm{h} $ (upper right), $ \tau_\mathrm{h}\tau_\mathrm{h} $ (lower left), and $ \mathrm{e}\mu $ (lower right) channels. The lower panels show ratios of the data to the pre-fit background prediction and post-fit background yields as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit uncertainty. The dashed lines correspond to the signal expectation for Z' boson masses of 1 TeV (black) and 2.5 TeV (magenta) decaying to $ \tau^{+}\tau^{-} $, normalized to cross sections of 199.4 fb and 0.7504 fb respectively. The dashed brown line corresponds to a Z' boson mass of 1.25 TeV decaying to W$^{+}$W$^{-}$, normalized to a cross section of 61.14 fb. The signal cross sections correspond to $ \{\kappa_{\mathrm{V}},g_{3},g_{1,\,2} \} = \{ 1,1,0\} $. |
png pdf |
Figure 1-d:
Observed $ m(\ell_{1},\ell_{2},p_{\mathrm{T}}^\text{miss}) $ for the data, and the post-fit backgrounds (stacked histograms), in the signal region for the $ \mu\tau_\mathrm{h} $ (upper left), $ \mathrm{e}\tau_\mathrm{h} $ (upper right), $ \tau_\mathrm{h}\tau_\mathrm{h} $ (lower left), and $ \mathrm{e}\mu $ (lower right) channels. The lower panels show ratios of the data to the pre-fit background prediction and post-fit background yields as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit uncertainty. The dashed lines correspond to the signal expectation for Z' boson masses of 1 TeV (black) and 2.5 TeV (magenta) decaying to $ \tau^{+}\tau^{-} $, normalized to cross sections of 199.4 fb and 0.7504 fb respectively. The dashed brown line corresponds to a Z' boson mass of 1.25 TeV decaying to W$^{+}$W$^{-}$, normalized to a cross section of 61.14 fb. The signal cross sections correspond to $ \{\kappa_{\mathrm{V}},g_{3},g_{1,\,2} \} = \{ 1,1,0\} $. |
png pdf |
Figure 2:
Combined 95% CL lower limits on $ m_{{\mathrm{Z}^{'}} } $ as a function of the Z' branching fraction to $ \tau^{+}\tau^{-} $ (upper row) and W$^{+}$W$^{-}$ (lower row) for the $ g_{1,\,2} = $ 0 (left column) and $ g_{1,\,2} = $ 1 (right column) scenario. The red, green, and blue curves show the observed limits corresponding to $ \kappa_{\mathrm{V}} $ equal to 0.1, 0.5, and 1, respectively. The dashed curves and shaded bands show the expected limits with their 68% CL percentile bands. |
png pdf |
Figure 2-a:
Combined 95% CL lower limits on $ m_{{\mathrm{Z}^{'}} } $ as a function of the Z' branching fraction to $ \tau^{+}\tau^{-} $ (upper row) and W$^{+}$W$^{-}$ (lower row) for the $ g_{1,\,2} = $ 0 (left column) and $ g_{1,\,2} = $ 1 (right column) scenario. The red, green, and blue curves show the observed limits corresponding to $ \kappa_{\mathrm{V}} $ equal to 0.1, 0.5, and 1, respectively. The dashed curves and shaded bands show the expected limits with their 68% CL percentile bands. |
png pdf |
Figure 2-b:
Combined 95% CL lower limits on $ m_{{\mathrm{Z}^{'}} } $ as a function of the Z' branching fraction to $ \tau^{+}\tau^{-} $ (upper row) and W$^{+}$W$^{-}$ (lower row) for the $ g_{1,\,2} = $ 0 (left column) and $ g_{1,\,2} = $ 1 (right column) scenario. The red, green, and blue curves show the observed limits corresponding to $ \kappa_{\mathrm{V}} $ equal to 0.1, 0.5, and 1, respectively. The dashed curves and shaded bands show the expected limits with their 68% CL percentile bands. |
png pdf |
Figure 2-c:
Combined 95% CL lower limits on $ m_{{\mathrm{Z}^{'}} } $ as a function of the Z' branching fraction to $ \tau^{+}\tau^{-} $ (upper row) and W$^{+}$W$^{-}$ (lower row) for the $ g_{1,\,2} = $ 0 (left column) and $ g_{1,\,2} = $ 1 (right column) scenario. The red, green, and blue curves show the observed limits corresponding to $ \kappa_{\mathrm{V}} $ equal to 0.1, 0.5, and 1, respectively. The dashed curves and shaded bands show the expected limits with their 68% CL percentile bands. |
png pdf |
Figure 2-d:
Combined 95% CL lower limits on $ m_{{\mathrm{Z}^{'}} } $ as a function of the Z' branching fraction to $ \tau^{+}\tau^{-} $ (upper row) and W$^{+}$W$^{-}$ (lower row) for the $ g_{1,\,2} = $ 0 (left column) and $ g_{1,\,2} = $ 1 (right column) scenario. The red, green, and blue curves show the observed limits corresponding to $ \kappa_{\mathrm{V}} $ equal to 0.1, 0.5, and 1, respectively. The dashed curves and shaded bands show the expected limits with their 68% CL percentile bands. |
| Summary |
| In summary, a first search for a heavy neutral spin-1 gauge boson Z' produced via vector boson fusion processes has been performed using data collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The search considers nonuniversal couplings of Z' bosons to fermions, including scenarios with dominant couplings to the third generation. Two decay channels, $ {\mathrm{Z}^{'}} \to\tau^{+}\tau^{-} $ and $ {\mathrm{Z}^{'}} \to\mathrm{W^+}\mathrm{W^-} $, are investigated. The invariant mass of the dilepton pair plus missing transverse momentum is used to search for the presence of a signal as a broad enhancement above the background expectation. The data are found to be in agreement with standard model predictions. In Z' models with nonuniversal fermion couplings, in particular those with Z' bosons having enhanced couplings to the third generation, the presence of Z' bosons decaying to a $ \tau $ lepton (W boson) pair is excluded for Z' masses up to 2.45 (1.60) TeV, depending on the Z' boson coupling to SM weak bosons and assuming a $ {\mathrm{Z}^{'}} \to\tau^{+}\tau^{-} $ (W$^{+}$W$^{-}$) branching fraction of 50%. These are the first limits on these models to date. |
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