CMS-SUS-16-037

CMS-SUS-16-037 ; CERN-EP-2017-088
Search for supersymmetry in pp collisions at $ \sqrt{s} = $ 13 TeV in the single-lepton final state using the sum of masses of large-radius jets
CMS Collaboration
12 May 2017
Phys. Rev. Lett. 119 (2017) 151802
Abstract: Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single lepton; multiple jets, including at least one b-tagged jet; and large missing transverse momentum. The search uses a sample of proton-proton collision data at $ \sqrt{s} = $ 13 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The observed event yields in the signal regions are consistent with those expected from standard model backgrounds. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production, with gluino decay into either on- or off-mass-shell top squarks. Assuming that the top squarks decay into a top quark plus a stable, weakly interacting neutralino, scenarios with gluino masses up to about 1.9 TeV are excluded at 95% confidence level for neutralino masses up to about 1 TeV.
Links: e-print arXiv:1705.04673 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	Additional Figures & Tables	References	CMS Publications

Additional information on efficiencies needed for reinterpretation of these results are available here.
Additional technical material for CMS speakers can be found here.

Figures
png pdf	Figure 1: Distributions of ${M_J}$ observed in data for 200 $ < { {p_{\mathrm {T}}} ^\text {miss}} \leq $ 350 GeV (left) and $ { {p_{\mathrm {T}}} ^\text {miss}} > $ 350 GeV (right) with the baseline selection and either $ {m_{\mathrm {T}}} \leq $ 140 GeV or $ {m_{\mathrm {T}}} > $ 140 GeV. In each plot, the data at low $ {m_{\mathrm {T}}} $ have been normalized to the yield observed at high ${m_{\mathrm {T}}} $. The vertical dashed lines at $ {M_J} = $ 250 GeV and 400 GeV show the boundaries separating the control and signal regions. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\mathrm{ b } }} \geq $ 2. Two SUSY benchmark models, whose contributions are small in the lower $ { {p_{\mathrm {T}}} ^\text {miss}} $ region, are shown in the solid and dashed red histograms. Overflow events are included in the uppermost bins.
png pdf	Figure 1-a: Distribution of ${M_J}$ observed in data for 200 $ < { {p_{\mathrm {T}}} ^\text {miss}} \leq $ 350 GeV with the baseline selection and either $ {m_{\mathrm {T}}} \leq $ 140 GeV or $ {m_{\mathrm {T}}} > $ 140 GeV. The data at low $ {m_{\mathrm {T}}} $ have been normalized to the yield observed at high ${m_{\mathrm {T}}} $. The vertical dashed lines at $ {M_J} = $ 250 GeV and 400 GeV show the boundaries separating the control and signal regions. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\mathrm{ b } }} \geq $ 2. Two SUSY benchmark models, whose contributions are small in the lower $ { {p_{\mathrm {T}}} ^\text {miss}} $ region, are shown in the solid and dashed red histograms. Overflow events are included in the uppermost bin.
png pdf	Figure 1-b: Distributions of ${M_J}$ observed in data for $ { {p_{\mathrm {T}}} ^\text {miss}} > $ 350 GeV with the baseline selection and either $ {m_{\mathrm {T}}} \leq $ 140 GeV or $ {m_{\mathrm {T}}} > $ 140 GeV. The data at low $ {m_{\mathrm {T}}} $ have been normalized to the yield observed at high ${m_{\mathrm {T}}} $. The vertical dashed lines at $ {M_J} = $ 250 GeV and 400 GeV show the boundaries separating the control and signal regions. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\mathrm{ b } }} \geq $ 2. Two SUSY benchmark models, whose contributions are small in the lower $ { {p_{\mathrm {T}}} ^\text {miss}} $ region, are shown in the solid and dashed red histograms. Overflow events are included in the uppermost bin.
png pdf root	Figure 2: Excluded gluino and neutralino masses at 95% CL for the T1tttt (black, dark solid) and T5tttt (blue, light solid) models. The dashed red lines show the expected exclusion for the T1tttt model. The color map shows the observed cross section upper limits for the T1tttt model. The theoretical uncertainties in the T5tttt exclusion curve are similar to those for T1tttt.

Tables
png pdf	Table 1: Observed event yields and mean background yields from the predictive fit in the 18 bins of the signal region R4. Each bin is specified by the values of $ { {p_{\mathrm {T}}} ^\text {miss}} $, $ {N_{\text {jets}}} $. and $ {N_{\mathrm{ b } }} $. The uncertainties in $\kappa $ include both a statistical component from the size of the MC samples and a systematic component assessed from the data control samples. The uncertainty in the predicted event yield includes both of these and the statistical uncertainties associated with the data control regions. Yields for the two T1tttt benchmark models NC and C are also given.
png pdf	Table 2: Observed event yields and mean background yields from the predictive fit in four aggregate search bins. In all four cases, the predicted yields refer to the signal region R4 with the standard $ {m_{\mathrm {T}}} > $ 140 GeV and $ {M_J} > $ 400 GeV requirements applied in addition to the baseline selection. Unlike the finely binned approach, where all 18 background predictions are computed simultaneously, the four aggregate bin predictions are computed separately. The aggregate bins overlap, causing their background predictions to be highly correlated. Yields for the two T1tttt benchmark models NC and C are also given.

Summary

In summary, we have performed a search for an excess event yield above that expected for standard model (SM) processes using a data sample of proton-proton collision events with an integrated luminosity of 35.9 fb$^{-1}$ at $\sqrt{s} = $ 13 TeV. The signature is characterized by large missing transverse momentum, a single isolated lepton, multiple jets, and at least one b-tagged jet. No significant excesses above the SM backgrounds are observed. The results are interpreted in the framework of simplified models that describe natural supersymmetry (SUSY) scenarios. For gluino pair production followed by the three-body decay $\tilde{g} \to \mathrm{ t \bar{t} } \tilde{ \chi }^0_1$ (T1tttt model), gluinos with masses below 1.9 TeV are excluded at 95% confidence level for neutralino masses up to about 1 TeV. For the two-body gluino decay $ \tilde{g} \to \tilde{ \mathrm{t} }_1 \bar{ \mathrm{t} } $ with $ \tilde{ \mathrm{t} }_1 \to \mathrm{t} \tilde{ \chi }^0_1 $ (T5tttt model), the results are generally similar, except at low neutralino masses, where the excluded gluino mass is somewhat lower. These results extend previous gluino mass limits by about 300 GeV and are among the most stringent constraints on these simplified models of SUSY to date.

Additional Figures
png pdf root	Additional Figure 1: Covariance matrix for the expected backgrounds from the predictive fit.
png pdf root	Additional Figure 2: Correlation matrix for expected backgrounds from the predictive fit.
png pdf	Additional Figure 3: Observed significance in the T1tttt plane.
png pdf	Additional Figure 4: Observed significance in the T5tttt plane.
png pdf root	Additional Figure 5: Exclusion limits at 95% confidence level in the T5tttt plane.
png pdf	Additional Figure 6: Gluino pair production and decay for the simplified model T1tttt.
png pdf	Additional Figure 7: Gluino pair production and decay for the simplified model T5tttt.

Additional Tables
png pdf	Additional Table 1: Cutflow table. Rows above the single horizontal line are part of the "baseline selection.'' For the T1tttt and T5tttt signal models, (1800,100) denotes $m_{\text {gluino}}= $ 1800 GeV, $m_{\text {LSP}}= $ 100 GeV, while (1400,1000) denotes $m_{\text {gluino}}= $ 1400 GeV, $m_{\text {LSP}}= $ 1000 GeV.

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