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| CMS-EXO-15-006 ; CERN-EP-2016-281 | ||
| Search for heavy gauge W' bosons in events with an energetic lepton and large missing transverse momentum at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 29 December 2016 | ||
| Phys. Lett. B 770 (2017) 278 | ||
| Abstract: A search is presented for W' bosons in events with an electron or muon and large missing transverse momentum, using proton-proton collision data at $ \sqrt{s} = $ 13 TeV collected with the CMS detector in 2015 and corresponding to an integrated luminosity of 2.3 fb$^{-1}$. No evidence of an excess of events relative to the standard model expectations is observed. For a W' boson described by the sequential standard model, upper limits at 95% confidence level are set on the product of the production cross section and branching fraction and lower limits are established on the new boson mass. Masses below 4.1 TeV are excluded combining electron and muon decay channels, significantly improving upon the results obtained with the 8 TeV data. Exclusion limits at 95% confidence level on the product of the W' production cross section and branching fraction are also derived in combination with the 8 TeV data. Finally, exclusion limits are set for the production of generic W' bosons decaying into this final state using a model-independent approach. | ||
| Links: e-print arXiv:1612.09274 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Production and decay of an SSM W' boson. The final state shown denotes both the ($\overline {\ell }\nu _{\ell }$) state and its charge conjugate. |
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Figure 2:
Distributions for data and expected SM backgrounds in the electron channel: transverse mass ${M_\mathrm {T}}$ (left) and the associated integral distribution (total number of events above a given value of ${M_\mathrm {T}}$) (right). The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panels show the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 2-a:
Transverse mass ${M_\mathrm {T}}$ distribution for data and expected SM backgrounds in the electron channel. The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panel shows the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 2-b:
Integral distribution for data and expected SM backgrounds in the electron channel (total number of events above a given value of ${M_\mathrm {T}}$). The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panel shows the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 3:
Distributions for data and expected SM backgrounds in the muon channel: transverse mass ${M_\mathrm {T}}$ (left) and the associated integral distribution (total number of events above a given value of ${M_\mathrm {T}}$) (right). The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panels show the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 3-a:
Transverse mass ${M_\mathrm {T}}$ distribution for data and expected SM backgrounds in the muon channel. The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panel shows the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 3-b:
Integral distribution for data and expected SM backgrounds in the muon channel (total number of events above a given value of ${M_\mathrm {T}}$). The expected signals from the decays of W' bosons with masses $M(W') = $ 2.4 and 3.6 TeV are also shown in the left figure. The lower panel shows the ratio of data to SM predictions, where the band centered around unity indicates the systematic uncertainty in the expected background, excluding the 2.7% uncertainty in the luminosity. |
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Figure 4:
Expected and observed 95% CL limits for the electron (left) and muon (right) decay channels. The expected (observed) limit is displayed as a dashed (solid) line and the associated inner (outer) bands represent the one (two) standard deviation (s.d.) uncertainties. The SSM W' NNLO cross sections are displayed as a function of $M(W')$. |
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Figure 4-a:
Expected and observed 95% CL limits for the electron decay channel. The expected (observed) limit is displayed as a dashed (solid) line and the associated inner (outer) bands represent the one (two) standard deviation (s.d.) uncertainties. The SSM W' NNLO cross sections are displayed as a function of $M(W')$. |
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Figure 4-b:
Expected and observed 95% CL limits for the muon decay channel. The expected (observed) limit is displayed as a dashed (solid) line and the associated inner (outer) bands represent the one (two) standard deviation (s.d.) uncertainties. The SSM W' NNLO cross sections are displayed as a function of $M(W')$. |
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Figure 5:
Expected and observed 95% CL limits for the combination of the electron and muon decay channels. The expected (observed) limit is displayed as a dashed (solid) line and the associated inner (outer) bands represent the one (two) standard deviation (s.d.) uncertainties. The SSM W' NNLO cross section is displayed as a function of $M(W')$. |
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Figure 6:
Ratio of the cross section lower limit to the theoretical cross section shown in red (lighter curves) for the 8 TeV data, blue (darker curves) for the 13 TeV data, and black for the combined data sets in the electron (left) and muon (right) channels. The observed limits are shown with solid lines and expected limits with dashed lines. For the W' mass range 400-4000 GeV, where the combination is limited by the 8 TeV data set, the one- and two-standard deviation (s.d.) uncertainty bands for the combined limits are shown in green and yellow, respectively. |
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Figure 6-a:
Ratio of the cross section lower limit to the theoretical cross section shown in red (lighter curves) for the 8 TeV data, blue (darker curves) for the 13 TeV data, and black for the combined data sets in the electron channel. The observed limits are shown with solid lines and expected limits with dashed lines. For the W' mass range 400-4000 GeV, where the combination is limited by the 8 TeV data set, the one- and two-standard deviation (s.d.) uncertainty bands for the combined limits are shown in green and yellow, respectively. |
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Figure 6-b:
Ratio of the cross section lower limit to the theoretical cross section shown in red (lighter curves) for the 8 TeV data, blue (darker curves) for the 13 TeV data, and black for the combined data sets in the muon channel. The observed limits are shown with solid lines and expected limits with dashed lines. For the W' mass range 400-4000 GeV, where the combination is limited by the 8 TeV data set, the one- and two-standard deviation (s.d.) uncertainty bands for the combined limits are shown in green and yellow, respectively. |
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Figure 7:
Expected (dashed line) and observed (solid line) 95% CL limit for the model-independent cross section limit as a function of the lower ${M_\mathrm {T}}$ threshold, denoted ${M_\mathrm {T}^\mathrm {min}} $, for the electron channel (upper left), the muon channel (upper right), and the combined channels (bottom plot). The inner (outer) bands represent the one- (two-)standard deviation (s.d.) uncertainties. |
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Figure 7-a:
Expected (dashed line) and observed (solid line) 95% CL limit for the model-independent cross section limit as a function of the lower ${M_\mathrm {T}}$ threshold, denoted ${M_\mathrm {T}^\mathrm {min}} $, for the electron channel. The inner (outer) bands represent the one- (two-)standard deviation (s.d.) uncertainties. |
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Figure 7-b:
Expected (dashed line) and observed (solid line) 95% CL limit for the model-independent cross section limit as a function of the lower ${M_\mathrm {T}}$ threshold, denoted ${M_\mathrm {T}^\mathrm {min}} $, for the muon channel. The inner (outer) bands represent the one- (two-)standard deviation (s.d.) uncertainties. |
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Figure 7-c:
Expected (dashed line) and observed (solid line) 95% CL limit for the model-independent cross section limit as a function of the lower ${M_\mathrm {T}}$ threshold, denoted ${M_\mathrm {T}^\mathrm {min}} $, for the combined channels. The inner (outer) bands represent the one- (two-)standard deviation (s.d.) uncertainties. |
| Tables | |
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Table 1:
Numbers of events in the electron decay channel integrated above ${M_\mathrm {T}}$ thresholds of 500, 1000, and 1500 GeV, for data, SM background, and signals with M$(W') =$ 2.4 and 3.6 TeV . The uncertainties include systematic and statistical uncertainties, but do not include the 2.7% uncertainty in the integrated luminosity. |
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Table 2:
Numbers of events in the muon decay channel integrated above ${M_\mathrm {T}}$ thresholds of 500, 1000, and 1500 GeV, for data, SM background, and signals with M$(W')$ = 2.4 and 3.6 TeV . The uncertainties include statistical and systematic uncertainties, but do not include the 2.7% uncertainty in the integrated luminosity. |
| Summary |
| A search has been performed for sequential standard model W' bosons in final states containing a single energetic electron or muon and large missing transverse momentum, using proton-proton collision data at $ \sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 2.3 fb$^{-1}$. No deviation from the background expectations has been observed and exclusion limits at 95% confidence level have been extracted on the mass of a W' boson. Masses below 3.6 (3.9) TeV are excluded in the electron (muon) decay channel analysis, significantly improving upon the results obtained with the $ \sqrt{s} = $ 8 TeV data. This search has been combined with the earlier one conducted at $8 TeV$, where the sensitivity of the search is dominated by the 13 TeV data, yielding a lower mass limit of 4.1 TeV for W' bosons when combining data from both decay channels and center-of-mass energies. Finally, generic limits on the production of W' resonances with the same leptonic final states have been obtained using a model-independent approach. |
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