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| CMS-PAS-EXO-16-043 | ||
| Search for pair-production of first generation scalar leptoquarks in pp collisions at $ \sqrt{s} = $ 13 TeV with 2.6 fb$^{-1}$ | ||
| CMS Collaboration | ||
| August 2016 | ||
| Abstract: A search for pair production of first generation scalar leptoquarks is presented, considering a final state containing two electrons and at least two jets, using proton-proton collision data at $ \sqrt{s} = $ 13 TeV. The data were recorded with the CMS detector at the LHC during 2015, and correspond to an integrated luminosity of 2.6 fb$^{-1}$. First generation scalar leptoquarks with masses less than 1130 (920) GeV are excluded for $\beta = $ 1.0 ($\beta = $ 0.5), where $\beta$ is the branching fraction of a leptoquark decaying to a charged lepton and a quark. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1-a:
Distributions of ${p_{\mathrm {T}}}$ for the two leading electrons and two leading jets in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 1-b:
Distributions of ${p_{\mathrm {T}}}$ for the two leading electrons and two leading jets in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 1-c:
Distributions of ${p_{\mathrm {T}}}$ for the two leading electrons and two leading jets in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 1-d:
Distributions of ${p_{\mathrm {T}}}$ for the two leading electrons and two leading jets in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 2-a:
Distributions of the final selection variables ${S_{\mathrm {T}}}$, $M_{ee}$, and $M_{min}(ej)$, in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 2-b:
Distributions of the final selection variables ${S_{\mathrm {T}}}$, $M_{ee}$, and $M_{min}(ej)$, in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 2-c:
Distributions of the final selection variables ${S_{\mathrm {T}}}$, $M_{ee}$, and $M_{min}(ej)$, in the events passing preselection. Two leptoquark signal mass hypotheses are shown in addition to the data and background predictions. The category denoted as ``Other background'' includes single top, W+jets, diboson, and $\gamma $+jets events. |
png pdf |
Figure 3:
Observed and expected upper limits for scalar leptoquark pair-production cross section times $\beta ^2$ at the 95% confidence level. The median (dashed line), 1$\sigma $ (green), and 2$\sigma $ (yellow) expected limits are shown. The theoretical prediction is varied by the adjusting the renormalization and factorization scales and combining with the PDF uncertainty, to producing the shaded band. |
| Tables | |
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Table 1:
Scalar first-generation $LQ$ signal cross sections calculated at NLO. |
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Table 2:
Optimized final selection thresholds for the $eejj$ analysis. |
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Table 3:
Event yields after the optimized $eejj$ selections for signal, observed data, and background predictions. All uncertainties are statistical except for the total background, where statistical and systematic uncertainties are reported separately. |
| Summary |
| A search for pair production of first generation scalar leptoquarks has been presented, based on pp collision data collected in 2015 at $\sqrt{s} =$ 13 TeV and corresponding to an integrated luminosity of 2.6 $\text{fb}^{-1}$. The search considers the leptoquark decay into a final state containing two electrons and two jets. After background prediction is complete, the selection thresholds are optimized using a scan of the full parameter space for each leptoquark mass point. At each set of optimized selection thresholds, the number of observed events agrees with the background expectation based on standard model processes. Limits at 95% confidence level are set assuming $\beta = $ 1, excluding first generation scalar leptoquarks with masses less than 1130 GeV, compared to 1140 GeV for the median expected limit. Mass limits are also obtained for $\beta = $ 0.5, in which case first generation scalar leptoquarks with masses less than 920 GeV are excluded, with a median expected limit of 910 GeV. This is the tightest CMS constraint on the first generation scalar leptoquark mass to date. |
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