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| CMS-PAS-EXO-17-028 | ||
| Search for heavy Majorana neutrinos in the same-sign dilepton channel in proton-proton collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| March 2018 | ||
| Abstract: A search is performed for a heavy Majorana neutrino (N) decaying into a W boson and a lepton using the CMS detector at the LHC. A signature of two same-sign leptons and at least one jet is searched for using data collected during 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The data are found to be consistent with the expected standard model background. Upper limits are set, in the context of a Type I seesaw mechanism, on the cross section times branching fraction for production of a heavy Majorana neutrino in the mass range between 20 and 1600 GeV. The results are interpreted as limits on $|V_{\mathrm{e} \mathrm{N}}|^2$, $|V_{\mu \mathrm{N}}|^2$ and, $|V_{\mathrm{e} \mathrm{N}} V_{\mu \mathrm{N}}^*|^2 / (|V_{\mathrm{e} \mathrm{N}}|^2 + |V_{\mu \mathrm{N}}|^2)$, where $V_{\ell \mathrm{N}}$ is the matrix element describing the mixing of the heavy neutrino with the standard model neutrino of flavor $\ell = \mu,\,e$. In the mass range considered, the upper limits range between 2.3 $ \times 10^{-5}$ and unity. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 01 (2019) 122. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Current limits on $ {| {V_{\ell {\mathrm {N}}}} |}^2$ for $ {\mathrm {e}}$ (left) and $\mu $ (right), as well as the expected sensitivity from future experiments. Taken from Ref. [25]. |
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Figure 1-a:
Current limits on $ {| {V_{\ell {\mathrm {N}}}} |}^2$ for $ {\mathrm {e}}$ (left) and $\mu $ (right), as well as the expected sensitivity from future experiments. Taken from Ref. [25]. |
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Figure 1-b:
Current limits on $ {| {V_{\ell {\mathrm {N}}}} |}^2$ for $ {\mathrm {e}}$ (left) and $\mu $ (right), as well as the expected sensitivity from future experiments. Taken from Ref. [25]. |
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Figure 2:
Diagram representing a resonance production of a Majorana neutrino ($ {\mathrm {N}} $), via Drell-Yan (DY) $s$-channel process and its decay into same-sign leptons and two quarks. The charge-conjugate diagram results in a $\ell ^- \ell ^- \mathrm{ q \bar{q} }\prime $ final state. Taken from Ref. [35]. |
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Figure 3:
Diagram for photon-initiated processes for $ {\mathrm {q}}\gamma \to {\mathrm {N}} \ell ^{\pm} {\mathrm {q}}^{'}$. Taken from Ref. [35]. |
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Figure 4:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-a:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-b:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-c:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-d:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-e:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 4-f:
Kinematic distributions for the low-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 5:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-a:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-b:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-c:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-d:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-e:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
png pdf |
Figure 5-f:
Kinematic distributions for the high-mass signal region after all the selections are applied, except for the final optimization requirements in SR1 (left) and SR2 (right). The figures show the background predictions from prompt same-sign leptons (Prompt), misidentified leptons (Misid. lepton), mismeasured charge (Mismeas. charge) together with the number of events observed in data after combining the events in the $ {\mathrm {e}} {\mathrm {e}}$, $\mu \mu $, and $ {\mathrm {e}}\mu $ channels. |
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Figure 6:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-a:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-b:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-c:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-d:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-e:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 6-f:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the low-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7-a:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7-b:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
png pdf |
Figure 7-c:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7-d:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7-e:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 7-f:
Observed event yields and estimated backgrounds after the application of all selections for each Majorana neutrino mass signal region for the high-mass SR1 (left) and SR2 (right). The background predictions from prompt same-sign leptons (Prompt bkgd.), misidentified leptons (Misid. bkgd.), and mismeasured charge (Charge mismeas. bkgd.) are included together with the number of events observed in data. The uncertainties shown are the combined quadrature of statistical and systematic uncertainties. |
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Figure 8:
Exclusion region at 95% CL in the $ {| {V_{{\mathrm {e}} {\mathrm {N}}}} |}^2$ vs. $ {m_\mathrm {N}} $ plane. The dashed black curve is the expected upper limit, with one and two standard-deviation bands shown in dark green and light yellow, respectively. The solid black curve is the observed upper limit. Also shown are the upper limits from other direct searches: DELPHI [26], L3 [27,28], ATLAS [32], and the upper limits from the CMS $\sqrt {s} = $ 8 TeV 2012 data [31] and the trilepton analysis [36] based on the same 2016 data set as used in this analysis. |
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Figure 9:
Exclusion region at 95% CL in the $ {| {V_{\mu {\mathrm {N}}}} |}^2$ vs. $ {m_\mathrm {N}} $ plane. The dashed black curve is the expected upper limit, with one and two standard-deviation bands shown in dark green and light yellow, respectively. The solid black curve is the observed upper limit. Also shown are the upper limits from other direct searches: DELPHI [26], L3 [27,28], ATLAS [32], and the upper limits from the CMS $\sqrt {s} = $ 8 TeV 2012 data [31] and the trilepton analysis [36] based on the same 2016 data set as used in this analysis. |
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Figure 10:
Exclusion region at 95% CL in the $ {| {V_{{\mathrm {e}} {\mathrm {N}}}} {V^{*}_{\mu {\mathrm {N}}}} |}^2 / ({| {V_{{\mathrm {e}} {\mathrm {N}}}} |}^2 + {| {V_{\mu {\mathrm {N}}}} |}^2)$ vs. $ {m_\mathrm {N}} $ plane. The dashed black curve is the expected upper limit, with one and two standard-deviation bands shown in dark green and light yellow, respectively. The solid black curve is the observed upper limit. Also shown are the upper limits from the CMS $\sqrt {s} = $ 8 TeV 2012 data [31]. |
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Figure 11:
Comparison of the observed 95% CL exclusion regions for $| {V_{{\mathrm {e}} {\mathrm {N}}}} |^2$, $| {V_{\mu {\mathrm {N}}}} |^2$, and $ {| {V_{{\mathrm {e}} {\mathrm {N}}}} {V^{*}_{\mu {\mathrm {N}}}} |}^2 / (| {V_{{\mathrm {e}} {\mathrm {N}}}} |^2 + | {V_{\mu {\mathrm {N}}}} |^2)$. |
| Tables | |
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Table 1:
Selection requirements for the low- and high-mass search regions. |
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Table 2:
Observed event yields and estimated backgrounds in the control regions. The uncertainty in the background yield is the sum in quadrature of the statistical and systematic uncertainties. |
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Table 3:
Summary of the relative systematic uncertainties in heavy Majorana neutrino signal yields and in the background from prompt same-sign leptons, both estimated from simulation. The relative systematic uncertainties assigned to the misidentified-lepton and mismeasured-charge backgrounds estimated from control regions in data are also shown. The uncertainties are given for the low-mass (high-mass) selections. The range given for each systematic uncertainty source covers the variation across the mass range. |
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Table 4:
Summary of contributions to the systematic uncertainty related to the prompt same-sign lepton, misidentified-lepton, and mismeasured-charge backgrounds to the total background uncertainty. The numbers are for the SR1 (SR2) for the case of ${m_\mathrm {N}} = $ 50 and 500 GeV. |
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Table 5:
Observed event yields and estimated backgrounds after the application of all selections, except for the final optimization. The background predictions from prompt same-sign lepton (Prompt bkgd.), misidentified leptons (Misid. bkgd.), mismeasured charge (Charge mismeas. bkgd.) and the total background (Total bkgd.) are shown together with the number of events observed in data. The uncertainties shown are the statistical and systematic components, respectively. The "-'' indicates that the background is considered negligible. |
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Table 6:
Number of expected signal events after all the selections are applied. The matrix element $|{\mathrm V_{\ell N}}|$ is equal to $1 \times 10^{-4}$, $1 \times 10^{-2}$, and 1 for $ {m_\mathrm {N}} = $ 50 GeV, $ {m_\mathrm {N}} = $ 200 GeV, and $ {m_\mathrm {N}} = $ 1000 GeV respectively. |
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Table 7:
Selection requirements on discriminating variables determined by the optimization for each Majorana neutrino mass point. The last column shows the overall signal acceptance for $s$-channel. The uncertainties shown are statistical only. |
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Table 8:
Selection requirements on discriminating variables determined by the optimization for each Majorana neutrino mass point in the high-mass SR1. The last column shows the overall signal acceptance for $s$-channel [Numbers in bracket for for $t$-channel]. The uncertainties shown are statistical only. The "-'' indicates that no selection requirement is made. |
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Table 9:
Selection requirements on discriminating variables determined by the optimization for each Majorana neutrino mass point in the high-mass SR2. The last column shows the overall signal acceptance for $s$-channel [Numbers in bracket for for $t$-channel]. The uncertainties shown are statistical only. The "-'' indicates that no selection requirement is made. |
| Summary |
| A search for heavy Majorana neutrinos in the final states with same-sign dileptons and jet(s) has been performed in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data set corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess of events compared to the expected standard model background prediction is observed. Upper limits at 95% CL are set on the mixing matrix element between standard model neutrinos and heavy Majorana neutrino ($ |{{V_{\ell \mathrm{N}}} }$), as a function of heavy Majorana neutrino mass, ${m_\mathrm{N}} $. The analysis improved on previous searches by adding single-jet events into the signal region, which improved sensitivities for the lowest and and highest mass regions. For ${m_\mathrm{N}} = $ 40 GeV the observed (expected) limits are $ |{{V_{\mathrm{e} \mathrm{N}}} }|^{2} < 9.5 (8.0) \times 10^{-5}$, $ |{{V_{\mu \mathrm{N}}} }|^{2} < 2.0 (2.4) \times 10^{-5}$, and $ |{{V_{\mathrm{e} \mathrm{N}}} {V^{*}_{\mu \mathrm{N}}} }^2 / ( |{{V_{\mathrm{e} \mathrm{N}}} }^2 + |{{V_{\mu \mathrm{N}}} }^2) < 2.74 (2.84) \times 10^{-5}$. While for ${m_\mathrm{N}} = $ 1000 GeV the limits are $ |{{V_{\mathrm{e} \mathrm{N}}} }|^{2} < 0.43 (0.32)$, $ |{{V_{\mu \mathrm{N}}} }|^{2} < 0.27 (0.16)$, and $ |{{V_{\mathrm{e} \mathrm{N}}} {V^{*}_{\mu \mathrm{N}}} }^2 / ( |{{V_{\mathrm{e} \mathrm{N}}} }^2 + |{{V_{\mu \mathrm{N}}} }^2) < 0.14 (0.13)$. The search is sensitive to masses of heavy neutrinos up to 1600 GeV. The limits on the mixing matrix elements were placed up to 1430 GeV for the $ |{{V_{\mu \mathrm{N}}} }|^{2}$, 1240 GeV for $ |{{V_{\mathrm{e} \mathrm{N}}} }|^{2}$, and 1600 GeV for $ |{{V_{\mathrm{e} \mathrm{N}}} {V^{*}_{\mu \mathrm{N}}} }^2 / ( |{{V_{\mathrm{e} \mathrm{N}}} }^2 + |{{V_{\mu \mathrm{N}}} }^2)$. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV. These are the first limits on the heavy neutrino mixing parameters with the standard model neutrinos for Majorana neutrino masses above 1200 GeV. |
| References | ||||
| 1 | Particle Data Group Collaboration | Review of particle physics | CPC 40 (2016) 100001 | |
| 2 | J. A. McCarthy | Search for double beta decay in Ca$ ^{48} $ | PR97 (1955) 1234 | |
| 3 | V. R. Lazarenko and S. Y. Luk'yanov | An Attempt to Detect Double Beta Decay in Ca$ ^{48} $ | Soviet Physics JETP 22 (1966) 521 | |
| 4 | P. Minkowski | $ \mu \to \mathrm{e} \gamma $ at a Rate of One Out of 1-Billion Muon Decays? | PLB 67 (1977) 421 | |
| 5 | M. Gell-Mann, P. Ramond, and R. Slansky | Supergravity: proceedings of the supergravity workshop at Stony Brook | in Supergravity: proceedings of the Supergravity Workshop at Stony Brook, P. Nieuwenhuizen and D. Freedman, eds., p. 315 North-Holland | |
| 6 | T. Yanagida | Proceedings of the workshop on the unified theory and the baryon number in the universe | in Proceedings of the Workshop on the Unified Theory and the Baryon Number in the Universe, O. Sawada and A. Sugamoto, eds., p. 95 National Laboratory for High Energy Physics (KEK) | |
| 7 | R. N. Mohapatra and G. Senjanovi\ifmmode \acutec\else \'c\fi | Neutrino Mass and Spontaneous Parity Violation | PRL 44 (1980) 912 | |
| 8 | J. Schechter and J. W. F. Valle | Neutrino masses in su(2) $ \bigotimes $ u(1) theories | PRD 22 (1980) 2227 | |
| 9 | R. E. Shrock | General theory of weak processes involving neutrinos. i. leptonic pseudoscalar-meson decays, with associated tests for, and bounds on, neutrino masses and lepton mixing | PRD 24 (1981) 1232 | |
| 10 | J. Schechter and J. W. F. Valle | Neutrino decay and spontaneous violation of lepton number | PRD 25 (1982) 774 | |
| 11 | M. Magg and C. Wetterich | Neutrino mass problem and gauge hierarchy | Physics Letters B 94 (1980) 61 | |
| 12 | R. N. Mohapatra and G. Senjanovi\ifmmode \acutec\else \'c\fi | Neutrino masses and mixings in gauge models with spontaneous parity violation | PRD 23 (1981) 165 | |
| 13 | R. Foot, H. Lew, X.-G. He, and G. Joshi | See-saw neutrino masses induced by a triplet of leptons | Zeitschrift f$\ddot\mathrmu$r Physik C Particles and Fields 44 (1989) 441 | |
| 14 | R. N. Mohapatra | Mechanism for understanding small neutrino mass in superstring theories | PRL 56 (1986) 561 | |
| 15 | R. N. Mohapatra and J. W. F. Valle | Neutrino mass and baryon-number nonconservation in superstring models | PRD 34 (1986) 1642 | |
| 16 | J. Bernab\'eu et al. | Lepton flavour non-conservation at high energies in a superstring inspired standard model | Physics Letters B 187 (1987) 303 | |
| 17 | M. Lindner and M. Weiser | Gauge coupling unification in left-right symmetric models | PLB 383 (1996) 405 | hep-ph/9605353 |
| 18 | T. Asaka, S. Blanchet, and M. Shaposhnikov | The nuMSM, dark matter and neutrino masses | PLB 631 (2005) 151 | hep-ph/0503065 |
| 19 | T. Asaka and M. Shaposhnikov | The nuMSM, dark matter and baryon asymmetry of the universe | PLB 620 (2005) 17 | hep-ph/0505013 |
| 20 | W.-Y. Keung and G. Senjanovic | Majorana Neutrinos And The Production Of The Right-Handed Charged Gauge Boson | PRL 50 (1983) 1427 | |
| 21 | D. A. Dicus, D. D. Karatas, and P. Roy | Lepton nonconservation at supercollider energies | PRD 44 (1991) 2033 | |
| 22 | A. Datta, M. Guchait, and A. Pilaftsis | Probing lepton number violation via majorana neutrinos at hadron supercolliders | PRD 50 (1994) 3195 | hep-ph/9311257 |
| 23 | F. M. L. Almeida, Y. A. Coutinho, J. A. M. Sim\ oes, and M. A. B. d. Vale | Signature for heavy majorana neutrinos in hadronic collisions | PRD 62 (2000) 075004 | hep-ph/0002024 |
| 24 | O. Panella, M. Cannoni, C. Carimalo, and Y. Srivastava | Signals of heavy Majorana neutrinos at hadron colliders | PRD 65 (2002) 035005 | hep-ph/0107308 |
| 25 | F. F. Deppisch, P. S. B. Dev, and A. Pilaftsis | Neutrinos and collider physics | New. J. Phys. 17 (2015) 075019 | |
| 26 | DELPHI Collaboration | Search for neutral heavy leptons produced in Z decays | Z. Phys. C 74 (1997) 57 | |
| 27 | L3 Collaboration | Search for isosinglet neutral heavy leptons in Z$ ^0 $ decays | PLB 295 (1992) 371 | |
| 28 | L3 Collaboration | Search for heavy isosinglet neutrino in $ \mathrm{e}^{+} \mathrm{e}^{-} $ annihilation at LEP | PLB 517 (2001) 67 | hep-ex/0107014 |
| 29 | LHCb Collaboration | Search for Majorana neutrinos in $ B^- \to \pi^+\mu^-\mu^- $ decays | PRL 112 (2014) 131802 | 1401.5361 |
| 30 | CMS Collaboration | Search for heavy Majorana neutrinos in $ \mu^\pm \mu^\pm+ $ jets events in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | PLB 748 (2015) 144 | CMS-EXO-12-057 1501.05566 |
| 31 | CMS Collaboration | Search for heavy Majorana neutrinos in ee+e$ \mu $ + jets events in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | JHEP 04 (2016) 169 | CMS-EXO-14-014 1603.02248 |
| 32 | ATLAS Collaboration | Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at $ \sqrt{s} = $ 8 TeV | JHEP 07 (2015) 162 | 1506.06020 |
| 33 | A. Atre, T. Han, S. Pascoli, and B. Zhang | The Search for Heavy Majorana Neutrinos | JHEP 05 (2009) 030 | 0901.3589 |
| 34 | P. S. B. Dev, A. Pilaftsis, and U.-k. Yang | New Production Mechanism for Heavy Neutrinos at the LHC | PRL 112 (2014), no. 8, 081801 | 1308.2209 |
| 35 | D. Alva, T. Han, and R. Ruiz | Heavy Majorana neutrinos from W$ \gamma $ fusion at hadron colliders | JHEP 02 (2015) 072 | 1411.7305 |
| 36 | CMS Collaboration | Search for heavy neutral leptons in events with three charged leptons in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | Submitted to \it PRLett | CMS-EXO-17-012 1802.02965 |
| 37 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 38 | J. Alwall et al. | The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations | JHEP 07 (2014) 079 | 1405.0301 |
| 39 | J. M. Campbell and R. K. Ellis | MCFM for the Tevatron and the LHC | NPPS 205-206 (2010) 10 | 1007.3492 |
| 40 | T. Melia, P. Nason, R. Rontsch, and G. Zanderighi | W+W-, WZ and ZZ production in the POWHEG BOX | JHEP 11 (2011) 078 | 1107.5051 |
| 41 | R. D. Ball et al. | Parton distributions for the lhc run ii | JHEP 04 (2015) 040 | 1410.8849 |
| 42 | T. Sj$\ddot\mathrmo$strand et al. | An Introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
| 43 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC 76 (2016) 155 | CMS-GEN-14-001 1512.00815 |
| 44 | GEANT4 Collaboration | GEANT4: A simulation toolkit | NIMA 506 (2003) 250 | |
| 45 | J. Alwall et al. | Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions | EPJC 53 (2008) 473 | 0706.2569 |
| 46 | R. Frederix and S. Frixione | Merging meets matching in MC@NLO | JHEP 12 (2012) 061 | 1209.6215 |
| 47 | P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietkerk | Automatic spin-entangled decays of heavy resonances in monte carlo simulations | Journal of High Energy Physics 2013 (2013) 15 | 1212.3460 |
| 48 | C. Degrande, O. Mattelaer, R. Ruiz, and J. Turner | Fully automated precision predictions for heavy neutrino production mechanisms at hadron colliders | PRD 94 (2016) 053002 | 1602.06957 |
| 49 | A. Manohar, P. Nason, G. P. Salam, and G. Zanderighi | How bright is the proton? a precise determination of the photon parton distribution function | PRL 117 (2016) 242002 | 1607.04266 |
| 50 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ k_T $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 51 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 52 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 53 | CMS Collaboration | Performance of Electron Reconstruction and Selection with the CMS Detector in Proton-Proton Collisions at $ \sqrt{s} = $ 8 TeV | JINST 10 (2015) P06005 | CMS-EGM-13-001 1502.02701 |
| 54 | CMS Collaboration | Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s} $~= 7 TeV | JINST 7 (2012) P10002 | CMS-MUO-10-004 1206.4071 |
| 55 | E. Akhmedov et al. | Improving Electro-Weak Fits with TeV-scale Sterile Neutrinos | JHEP 05 (2013) 081 | 1302.1872 |
| 56 | CMS Collaboration | Determination of Jet Energy Calibration and Transverse Momentum Resolution in CMS | JINST 6 (2011) P11002 | CMS-JME-10-011 1107.4277 |
| 57 | CMS Collaboration | Jet algorithms performance in 13 TeV data | CMS-PAS-JME-16-003 | CMS-PAS-JME-16-003 |
| 58 | S. D. Ellis, C. K. Vermilion, and J. R. Walsh | Techniques for improved heavy particle searches with jet substructure | PRD 80 (2009) 051501 | 0903.5081 |
| 59 | S. D. Ellis, C. K. Vermilion, and J. R. Walsh | Recombination algorithms and jet substructure: Pruning as a tool for heavy particle searches | PRD 81 (2010) 094023 | |
| 60 | CMS Collaboration | Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV | Submitted to \it JINST | CMS-BTV-16-002 1712.07158 |
| 61 | G. Punzi | Sensitivity of Searches for New Signals and its Optimization | in Statistical Problems in Particle Physics, Astrophysics, and Cosmology, L. Lyons, R. Mount, and R. Reitmeyer, eds., p. 79 2003 | physics/0308063 |
| 62 | CMS Collaboration | Performance of cms muon reconstruction in cosmic-ray events | JINST 5 (2010) T03022 | CMS-CFT-09-014 0911.4994 |
| 63 | A. Bierweiler, T. Kasprzik, and J. H. K$\ddot\mathrmu$hn | Vector-boson pair production at the LHC to $ \mathcal{O} $($ \alpha^{3} $) accuracy | JHEP 12 (2013) 071 | 1305.5402 |
| 64 | S. Gieseke, T. Kasprzik, and J. H. K$\ddot\mathrmu$hn | Vector-boson pair production and electroweak corrections in HERWIG++ | EPJC 74 (2014) 2988 | 1401.3964 |
| 65 | J. Baglio, L. D. Ninh, and M. M. Weber | Massive gauge boson pair production at the LHC: A next-to-leading order story | PRD 88 (2013) 113005 | 1307.4331 |
| 66 | CMS Collaboration | CMS Luminosity Measurements for the 2016 Data Taking Period | CMS-PAS-LUM-17-001 | CMS-PAS-LUM-17-001 |
| 67 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |
| 68 | T. Junk | Confidence level computation for combining searches with small statistics | NIMA 434 (1999) 435 | hep-ex/9902006 |
| 69 | A. L. Read | Presentation of search results: the cls technique | JPG 28 (2002) 2693 | |
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