CMS-PAS-SUS-16-037

CMS-PAS-SUS-16-037
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
March 2017

Abstract: Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single high transverse momentum lepton; multiple jets, including at least one b-tagged jet; and large missing transverse momentum. The search uses a 35.9 fb$^{-1}$ sample of proton-proton collision data at $\sqrt{s} =$ 13 TeV accumulated by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with those expected for 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 a 95% CL for neutralino masses up to about 1 TeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 119 (2017) 151802. The superseded preliminary plots can be found here.

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) in the 1$\ell $ data for low ($\leq $ 140 GeV) ${m_{\mathrm {T}}}$ and high ($>$ 140 GeV) $ {m_{\mathrm {T}}}$ regions. In each plot, the data at low $ {m_{\mathrm {T}}} $ have been renormalized to the yield observed at high $ {m_{\mathrm {T}}} $ to facilitate the comparison of the shapes of the distributions. The vertical dashed line at $ {M_J} = $ 250 GeV shows the lower boundary of regions R1 and R3, while the vertical line at $ {M_J} = $ 400 GeV separates R1 and R3 from R2 and R4. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\text {b}}} \geq $ 2. Two SUSY benchmark models are shown in the solid and dashed red histograms.
png pdf	Figure 1-a: Distribution of ${M_J}$ observed in data for 200 $ < { {p_{\mathrm {T}}} ^\text {miss}} \leq $ 350 GeV in the 1$\ell $ data for low ($\leq $ 140 GeV) ${m_{\mathrm {T}}}$ and high ($>$ 140 GeV) $ {m_{\mathrm {T}}}$ regions. The data at low $ {m_{\mathrm {T}}} $ have been renormalized to the yield observed at high $ {m_{\mathrm {T}}} $ to facilitate the comparison of the shapes of the distributions. The vertical dashed line at $ {M_J} = $ 250 GeV shows the lower boundary of regions R1 and R3, while the vertical line at $ {M_J} = $ 400 GeV separates R1 and R3 from R2 and R4. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\text {b}}} \geq $ 2. Two SUSY benchmark models are shown in the solid and dashed red histograms.
png pdf	Figure 1-b: Distribution of ${M_J}$ observed in data for $ { {p_{\mathrm {T}}} ^\text {miss}} > $ 350 GeV in the 1$\ell $ data for low ($\leq $ 140 GeV) ${m_{\mathrm {T}}}$ and high ($>$ 140 GeV) $ {m_{\mathrm {T}}}$ regions. The data at low $ {m_{\mathrm {T}}} $ have been renormalized to the yield observed at high $ {m_{\mathrm {T}}} $ to facilitate the comparison of the shapes of the distributions. The vertical dashed line at $ {M_J} = $ 250 GeV shows the lower boundary of regions R1 and R3, while the vertical line at $ {M_J} = $ 400 GeV separates R1 and R3 from R2 and R4. The data are integrated over $ {N_{\text {jets}}} \geq $ 6 and $ {N_{\text {b}}} \geq $ 2. Two SUSY benchmark models are shown in the solid and dashed red histograms.
png pdf	Figure 2: Left: excluded cross sections and SUSY particle masses for the T1tttt model. The color map indicates cross section time branching fraction upper limits at a 95% confidence level across the T1tttt mass plane. The black (red) line shows the observed (expected) exclusion of mass scenarios with theoretical cross sections higher than their respective upper limits. Limits are computed using the global fit. Right: comparison of the excluded gluino and LSP masses for the T1tttt and T5tttt models. The gluino mass limits are similar except at low $m_{ \tilde{\chi }^0_1} $.
png pdf root	Figure 2-a: Excluded cross sections and SUSY particle masses for the T1tttt model. The color map indicates cross section time branching fraction upper limits at a 95% confidence level across the T1tttt mass plane. The black (red) line shows the observed (expected) exclusion of mass scenarios with theoretical cross sections higher than their respective upper limits. Limits are computed using the global fit.
png pdf root	Figure 2-b: Comparison of the excluded gluino and LSP masses for the T1tttt and T5tttt models. The gluino mass limits are similar except at low $m_{ \tilde{\chi }^0_1} $.

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. The uncertainties in $\kappa $ include (in order) both a statistical component from the size of the MC samples and a systematic component assessed from data control samples. The uncertainty in the predicted event yield includes both these and the statistical uncertainties associated with the control regions in the data. Also shown are the expected signal yields for two SUSY benchmark models.
png pdf	Table 2: Observed event yields and mean background yields from a predictive fit in four aggregate search bins. In all four cases, the predicted yields refer to R4 with the usual requirements of $ {m_{\mathrm {T}}} > $ 140 GeV and $ {M_J} > $ 400 GeV applied in addition to the baseline selection. Unlike the finely binned approach, where all 18 background predictions are found simultaneously, the four aggregate bin predictions here are computed separately and may be highly correlated due to overlapping definitions.

Summary

In summary, we have performed a search for an excess event yield above that expected for 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 based on events with large missing transverse momentum, a single isolated lepton, multiple high pT jets, and at least one b-tagged jet. No significant excesses above the expected SM backgrounds is observed in any of the signal regions. The results are interpreted in the framework of simplified models that describe important natural SUSY scenarios with gluino pair production, followed by gluino decay into top quarks and a neutralino. For three-body decay, gluinos with masses below 1.9 TeV are excluded at a 95% CL for neutralino masses up to about 1 TeV. The results for two-body gluino decay are generally similar except at low neutralino masses, where the exclusion weakens. These results are among the most stringent constraints on these SUSY models 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.

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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