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| CMS-PAS-EXO-17-011 | ||
| 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 | ||
| December 2017 | ||
| Abstract: A search for a heavy right-handed W gauge boson and a heavy right-handed neutrino at the CERN LHC has been conducted by the CMS collaboration in events with two same-flavor leptons (e or $\mu$) and two jets, using 2016 proton-proton collision data corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No excess above the standard model expectation is seen in the invariant mass distribution of the dilepton plus dijet system. Assuming identical couplings and decay branching fractions as the standard model W gauge boson, 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 a 95% confidence level extends to approximately $m_{{\mathrm W}_R}= $ 4.4 TeV and covers a large range of neutrino masses below the ${\mathrm W}_R$ boson mass. This analysis provides the most stringent limits to date. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 05 (2018) 148. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Distribution of kinematic quantities for events in the low-dilepton mass control region. The four-object invariant mass (on the top) and the dilepton transverse momentum (on the bottom) for the DY $\mu \mu $ plus two jets selection are shown on the left. The dilepton mass (on the top) and the scalar sum of all jets $ {p_{\mathrm {T}}} $ (on the bottom) for the DY ee plus two jets selection are shown on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 1-a:
Distribution of kinematic quantities for events in the low-dilepton mass control region. The four-object invariant mass (on the top) and the dilepton transverse momentum (on the bottom) for the DY $\mu \mu $ plus two jets selection are shown on the left. The dilepton mass (on the top) and the scalar sum of all jets $ {p_{\mathrm {T}}} $ (on the bottom) for the DY ee plus two jets selection are shown on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 1-b:
Distribution of kinematic quantities for events in the low-dilepton mass control region. The four-object invariant mass (on the top) and the dilepton transverse momentum (on the bottom) for the DY $\mu \mu $ plus two jets selection are shown on the left. The dilepton mass (on the top) and the scalar sum of all jets $ {p_{\mathrm {T}}} $ (on the bottom) for the DY ee plus two jets selection are shown on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 1-c:
Distribution of kinematic quantities for events in the low-dilepton mass control region. The four-object invariant mass (on the top) and the dilepton transverse momentum (on the bottom) for the DY $\mu \mu $ plus two jets selection are shown on the left. The dilepton mass (on the top) and the scalar sum of all jets $ {p_{\mathrm {T}}} $ (on the bottom) for the DY ee plus two jets selection are shown on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 1-d:
Distribution of kinematic quantities for events in the low-dilepton mass control region. The four-object invariant mass (on the top) and the dilepton transverse momentum (on the bottom) for the DY $\mu \mu $ plus two jets selection are shown on the left. The dilepton mass (on the top) and the scalar sum of all jets $ {p_{\mathrm {T}}} $ (on the bottom) for the DY ee plus two jets selection are shown on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 2:
Kinematic distributions for events in the flavor control region. The dilepton mass (top left), the four-object mass (top right), the scalar sum of all jets $ {p_{\mathrm {T}}} $ (bottom left) and the number of jets (bottom right) are shown. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 2-a:
Kinematic distributions for events in the flavor control region. The dilepton mass (top left), the four-object mass (top right), the scalar sum of all jets $ {p_{\mathrm {T}}} $ (bottom left) and the number of jets (bottom right) are shown. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
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Figure 2-b:
Kinematic distributions for events in the flavor control region. The dilepton mass (top left), the four-object mass (top right), the scalar sum of all jets $ {p_{\mathrm {T}}} $ (bottom left) and the number of jets (bottom right) are shown. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
png |
Figure 2-c:
Kinematic distributions for events in the flavor control region. The dilepton mass (top left), the four-object mass (top right), the scalar sum of all jets $ {p_{\mathrm {T}}} $ (bottom left) and the number of jets (bottom right) are shown. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
png |
Figure 2-d:
Kinematic distributions for events in the flavor control region. The dilepton mass (top left), the four-object mass (top right), the scalar sum of all jets $ {p_{\mathrm {T}}} $ (bottom left) and the number of jets (bottom right) are shown. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. |
png pdf |
Figure 3:
Four-object mass distribution in the signal region for the electron channel on the left and for the muon channel on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. The gray error band around 1 represents instead the systematic uncertainty of the simulation. |
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Figure 3-a:
Four-object mass distribution in the signal region for the electron channel on the left and for the muon channel on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. The gray error band around 1 represents instead the systematic uncertainty of the simulation. |
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Figure 3-b:
Four-object mass distribution in the signal region for the electron channel on the left and for the muon channel on the right. The error bands on the MC histograms only include statistical uncertainties. The error bars in the ratio represent the statistical uncertainties of data and MC calculated with the standard error propagation of $\frac {N_d}{N_s}$ given $N_d$ the number of data events in the bin and $N_s$ the number of simulated events in the bin. The gray error band around 1 represents instead the systematic uncertainty of the simulation. |
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Figure 4:
Limit on $\sigma (pp\rightarrow \mathrm{W}_{R}) \times BR(\mathrm{W}_{R} \rightarrow \ell \ell \text {jj})$ with systematic uncertainties 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 regions containing, respectively, the 68% and 95% of the distribution of limits expected under the signal plus background hypothesis. Right-handed bosons with $m_{\mathrm{W}_{R}} < $ 4.4 TeV are excluded. |
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Figure 4-a:
Limit on $\sigma (pp\rightarrow \mathrm{W}_{R}) \times BR(\mathrm{W}_{R} \rightarrow \ell \ell \text {jj})$ with systematic uncertainties 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 regions containing, respectively, the 68% and 95% of the distribution of limits expected under the signal plus background hypothesis. Right-handed bosons with $m_{\mathrm{W}_{R}} < $ 4.4 TeV are excluded. |
png pdf |
Figure 4-b:
Limit on $\sigma (pp\rightarrow \mathrm{W}_{R}) \times BR(\mathrm{W}_{R} \rightarrow \ell \ell \text {jj})$ with systematic uncertainties 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 regions containing, respectively, the 68% and 95% of the distribution of limits expected under the signal plus background hypothesis. Right-handed bosons with $m_{\mathrm{W}_{R}} < $ 4.4 TeV are excluded. |
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Figure 5:
Upper limit on the cross section for different $ \mathrm{W}_{R} $ and ${{{\mathrm N}_R}}$ mass hypothesis, 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 containing the 68% of the distribution of limits expected under the signal plus background hypothesys. |
png pdf |
Figure 5-a:
Upper limit on the cross section for different $ \mathrm{W}_{R} $ and ${{{\mathrm N}_R}}$ mass hypothesis, 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 containing the 68% of the distribution of limits expected under the signal plus background hypothesys. |
png pdf |
Figure 5-b:
Upper limit on the cross section for different $ \mathrm{W}_{R} $ and ${{{\mathrm N}_R}}$ mass hypothesis, 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 containing the 68% of the distribution of limits expected under the signal plus background hypothesys. |
| Tables | |
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Table 1:
Transfer factor applied to the number of events in flavor control region to estimate the number of ${\mathrm{t} {}\mathrm{\bar{t}}}$ events in the $\mathrm{e} \mathrm{e} \text {jj}$ and $\mu \mu \text {jj}$ signal regions. |
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Table 2:
Effect of object reconstruction's systematic uncertainties on signal and background yields. |
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Table 3:
Uncertainties affecting $m_{\ell \ell \text {jj}}$ shape and normalization. The $ {\mathrm{t} {}\mathrm{\bar{t}}} $ SFs affect the $ {\mathrm{t} {}\mathrm{\bar{t}}} $ background, the DY PDF, factorization, and renormalization scales affect the DY + jets background and the luminosity affects both signal and backgrounds. |
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Table 4:
Observed number of events and magnitudes of systematic and statistical uncertainties for the expected events in different $ \mathrm{W}_{R} $ mass windows. All uncertainties are in number of events. In each table cell, the entry is of the form (mean $\pm $ stat. $\pm $ syst.). |
| Summary |
| In summary, a search for a right-handed W analogue to the W gauge boson in the decay channel of two leptons and two jets has been presented. No excess over standard model backgrounds are observed. A new W boson-like particle, with standard model couplings, decaying via a new heavy neutrino, up to a mass of 4.4 TeV, is excluded at 95% confidence level by the data, providing the most stringent limits to date. |
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