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| CMS-PAS-EXO-18-005 | ||
| Search for vector-like leptons in multilepton final states in pp collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| July 2018 | ||
| Abstract: A search for an SU(2) doublet of vector-like leptons with preferential couplings to the third generation standard model leptons is presented studying multilepton final states. The data sample corresponds to 41.4 fb$^{-1}$ of integrated luminosity in pp collisions at $\sqrt{s} = $ 13 TeV collected by the CMS experiment at the Large Hadron Collider in 2017. Events are categorized based on the multiplicity of light leptons and taus. The missing transverse momentum and the scalar sum of transverse momenta of leptons are used to discriminate the signal against standard model backgrounds. The observations are consistent with the expectations from the standard model processes. These results are used to exclude vector-like leptons in the mass range of 130-690 GeV. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRD. 100 (2019) 052003. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Associated production of ($ {\tau}'$, $ {\nu _{\tau}}'$) pairs via an off-shell W (left) and Z (right) boson, as well as possible subsequent decay chains that result in multileptonic final states. |
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Figure 1-a:
Associated production of ($ {\tau}'$, $ {\nu _{\tau}}'$) pairs via an off-shell W (left) and Z (right) boson, as well as possible subsequent decay chains that result in multileptonic final states. |
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Figure 1-b:
Associated production of ($ {\tau}'$, $ {\nu _{\tau}}'$) pairs via an off-shell W (left) and Z (right) boson, as well as possible subsequent decay chains that result in multileptonic final states. |
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Figure 2:
The ${\textrm {L}_\textrm {T}}$ distribution in a WZ enriched selection of events with three light leptons and one OSSF pair with mass on-Z, 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $100 GeV (left), and the $ M_{4\ell}$ distribution in a ZZ enriched selection of events with four light leptons and two OSSF pairs both of which are on-Z, and $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes after applying the respective normalization factors. The gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 2-a:
The ${\textrm {L}_\textrm {T}}$ distribution in a WZ enriched selection of events with three light leptons and one OSSF pair with mass on-Z, 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $100 GeV (left), and the $ M_{4\ell}$ distribution in a ZZ enriched selection of events with four light leptons and two OSSF pairs both of which are on-Z, and $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes after applying the respective normalization factors. The gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 2-b:
The ${\textrm {L}_\textrm {T}}$ distribution in a WZ enriched selection of events with three light leptons and one OSSF pair with mass on-Z, 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $100 GeV (left), and the $ M_{4\ell}$ distribution in a ZZ enriched selection of events with four light leptons and two OSSF pairs both of which are on-Z, and $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes after applying the respective normalization factors. The gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 3:
The light lepton pair mass distribution in a fake tau enriched selection of events with 2 OS e/$ {{\mu}}$ +$ {\tau}$, $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left), and the ${\textrm {M}_\textrm {T}}$ distribution in a selection of events with three light leptons and one OSSF pair with mass on-Z, ${E_{\mathrm {T}}^{\text {miss}}} < $ 100 GeV (right). The total SM background is shown as a stack of all contributing processes, and the gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 3-a:
The light lepton pair mass distribution in a fake tau enriched selection of events with 2 OS e/$ {{\mu}}$ +$ {\tau}$, $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left), and the ${\textrm {M}_\textrm {T}}$ distribution in a selection of events with three light leptons and one OSSF pair with mass on-Z, ${E_{\mathrm {T}}^{\text {miss}}} < $ 100 GeV (right). The total SM background is shown as a stack of all contributing processes, and the gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 3-b:
The light lepton pair mass distribution in a fake tau enriched selection of events with 2 OS e/$ {{\mu}}$ +$ {\tau}$, $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left), and the ${\textrm {M}_\textrm {T}}$ distribution in a selection of events with three light leptons and one OSSF pair with mass on-Z, ${E_{\mathrm {T}}^{\text {miss}}} < $ 100 GeV (right). The total SM background is shown as a stack of all contributing processes, and the gray band in the lower panel represents the statistical uncertainty on the expected background. The highest bin includes overflow events. |
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Figure 4:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with three light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
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Figure 4-a:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with three light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
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Figure 4-b:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with three light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
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Figure 5:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with four or more light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 5-a:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with four or more light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 5-b:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with four or more light leptons with $ {E_{\mathrm {T}}^{\text {miss}}} < $ 50 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 50 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 6:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with two opposite charge light leptons and a hadronically decaying $\tau $ lepton with 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 6-a:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with two opposite charge light leptons and a hadronically decaying $\tau $ lepton with 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 6-b:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with two opposite charge light leptons and a hadronically decaying $\tau $ lepton with 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
png pdf |
Figure 7:
The $ {\textrm {L}_\textrm {T}} $ distribution for events with two same charge light leptons and a hadronically decaying $\tau $ lepton with 50 $ < {E_{\mathrm {T}}^{\text {miss}}} < $ 150 GeV (left) and with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 150 GeV (right). The total SM background is shown as a stack of all contributing processes. The predictions for signal models with $m_{\tau '/\nu '} = $ 300 GeV and $m_{\tau '/\nu '} = $ 500 GeV (sum of all production and decay modes) are also shown as solid lines. The hatched gray band in the upper panel, and the dark and light gray bands in the lower panel represent the total, statistical, and systematic uncertainties on the expected background, respectively. The highest bin includes overflow events. |
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Figure 8:
The 95% confidence level upper limits on the cross section for production of VLL pairs ($\tau '^{+} \tau '^{-}$, $\tau '^{\pm} \nu '$ and $\nu ' \nu '$). Also shown is the theoretical prediction for the cross section of the VLL production. The observed (expected) exclusion limit on the masses of vector-like leptons is in the range of 130-690 (110-560) GeV. |
| Tables | |
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Table 1:
Signal regions as defined in this analysis. The on-Z (below-Z) selection is defined as an OSSF lepton pair with mass between 76 and 106 GeV (less than 76 GeV). |
| Summary |
| In summary, we performed a search for vector-like leptons in multilepton final states using 41.4 fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = $ 13 TeV, collected using the CMS detector in 2017. We observe no significant discrepancies between the background prediction and the data. We exclude, at 95% confidence level, vector-like leptons with masses above 130 GeV and below 690 GeV. |
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Compact Muon Solenoid LHC, CERN |
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