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| CMS-EXO-17-011 ; CERN-EP-2018-028 | ||
| Search for a heavy right-handed W boson and a heavy neutrino in events with two same-flavor leptons and two jets at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 29 March 2018 | ||
| JHEP 05 (2018) 148 | ||
| Abstract: A search for a heavy right-handed W boson ($ \mathrm{ W_R } $) decaying to a heavy right-handed neutrino and a charged lepton in events with two same-flavor leptons (e or $ \mu $) and two jets, is presented. The analysis is based on proton-proton collision data, collected by the CMS Collaboration at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess above the standard model expectation is seen in the invariant mass distribution of the dilepton plus dijet system. Assuming that couplings are identical to those of the standard model, and that only one heavy neutrino flavor ${\mathrm {N_R}}$ contributes significantly to the $ \mathrm{ W_R } $ decay width, the region in the two-dimensional ($ {m_{ \mathrm{ W_R } }} $, $ {m_{{\mathrm {N_R}} }} $) mass plane excluded at 95% confidence level extends to approximately ${m_{ \mathrm{ W_R } }} = $ 4.4 TeV and covers a large range of right-handed neutrino masses below the $ \mathrm{ W_R } $ boson mass. This analysis provides the most stringent limits on the $ \mathrm{ W_R } $ mass to date. | ||
| Links: e-print arXiv:1803.11116 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Kinematic distributions for events in the low dilepton mass control region with the DY SF applied. The dilepton mass (upper) and the scalar sum of all jet transverse momenta (lower) for the ee DY plus two jets selection are shown on the left. The $ {m_{\ell \ell \text {jj}}} $ (upper) and the dilepton transverse momentum (lower) for the $ {\mu} {\mu} $ DY plus two jets selection are shown on the right. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. |
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Figure 1-a:
Dilepton mass distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 1-b:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 1-c:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 1-d:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 2:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the electron (left) and muon (right) channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. |
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Figure 2-a:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the electron channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 2-b:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the muon channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 3:
Kinematic distributions for events in the flavor control region with the DY SF applied. The dilepton mass (upper left), the $ {m_{\ell \ell \text {jj}}} $ (upper right), the scalar sum of all jet transverse momenta (lower left), and the number of jets (lower right) are shown. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. |
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Figure 3-a:
The dilepton mass distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 3-b:
The $ {m_{\ell \ell \text {jj}}} $ sdistribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 3-c:
The scalar sum of all jet transverse momenta distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 3-d:
The number of jets distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. |
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Figure 4:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the electron (left) and muon (right) channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. |
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Figure 4-a:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the electron channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. |
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Figure 4-b:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the muon channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. |
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Figure 5:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the electron channel on the left and for the muon channel on the right. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. |
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Figure 5-a:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the electron channel. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. |
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Figure 5-b:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the muon channel. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. |
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Figure 6:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the electron channel on the left and for the muon channel on the right. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thin-dotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. |
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Figure 6-a:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the electron channel. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thin-dotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. |
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Figure 6-b:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the muon channel. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thin-dotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. |
| Tables | |
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Table 1:
Transfer factors applied to the number of events in the flavor control region to estimate the number of $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events in the $ {{\mathrm {e}} {\mathrm {e}}\text {jj}} $ and $ {{\mu} {\mu} \text {jj}}$ signal regions. |
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Table 2:
Effect of systematic uncertainties in candidate reconstruction efficiencies, energy scale and resolutions on the signal and background yields. The Signal column shows the range of uncertainties computed at each of the $ {\mathrm {W_R}} $ mass points. The Background column indicates the range of the uncertainties for the different backgrounds. |
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Table 3:
Uncertainties affecting the $ {m_{\ell \ell \text {jj}}} $ distribution shape and normalization. The uncertainties in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ SFs affect the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ background, the uncertainties in the DY PDF and the DY factorization and renormalization scales affect the DY+jets background, and the uncertainty in the integrated luminosity affects both signal and backgrounds. |
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Table 4:
Number of expected events for signal, DY+jets, $ {{\mathrm {t}\overline {\mathrm {t}}}} $, Other, and All backgrounds, as well as the observed number of events in different $ {\mathrm {W_R}} $ mass windows. All uncertainties are included in the expected number of events. In each table cell, the entry is of the form (mean $\pm $ stat $\pm $ syst). |
| Summary |
| A search for a right-handed analogue of the standard model W boson in the decay channel of two leptons and two jets has been presented. The analysis is based on proton-proton collision data collected at $\sqrt{s} = $ 13 TeV by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess over the standard model background expectations is observed in the invariant mass distribution of the dilepton plus dijet system. Thus the 2.8$\sigma$ excess previously observed in data recorded by CMS at 8 TeV is not confirmed. Assuming that couplings are identical to those of the standard model, a region in the two-dimensional plane ($ {m_{ \mathrm{ W_R } }} $, $ {m_{{\mathrm {N_R}} }} $) covering a large range of right-handed neutrino masses is excluded at 95% confidence level. A $ \mathrm{ W_R } $ boson decaying into a right-handed heavy neutrino with a mass ${m_{{\mathrm {N_R}} }}=1/2 {m_{\mathrm{ W_R }}}$ is excluded at 95% confidence level up to a mass of 4.4 TeV, providing the most stringent limit to date. |
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Compact Muon Solenoid LHC, CERN |
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