CMS-PAS-SUS-18-002 | ||
Search for supersymmetry in events with a photon, jets, and missing transverse momentum in proton-proton collisions at 13 TeV | ||
CMS Collaboration | ||
September 2018 | ||
Abstract: A search for supersymmetry is presented based on events with at least one photon, multiple jets, and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of √s= 13 TeV. The data correspond to an integrated luminosity of 35.9 fb−1 and were recorded by the CMS detector in 2016 at the LHC. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of b-tagged jets, and missing transverse momentum. No significant excess of events is observed with respect to expectations from standard model processes. Limits are placed on gluino, top squark, and neutralino masses using several simplified models of pair production of supersymmetric particles with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, gluino masses as large as 2120 GeV and top squark masses as large as 1230 GeV are excluded. | ||
Links:
CDS record (PDF) ;
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These preliminary results are superseded in this paper, EPJC 79 (2019) 444. The superseded preliminary plots can be found here. |
Figures | |
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Figure 1:
Example Feynman diagrams depicting the simplified models used. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model. |
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Figure 1-a:
Example Feynman diagrams depicting the simplified models used. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model. |
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Figure 1-b:
Example Feynman diagrams depicting the simplified models used. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model. |
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Figure 1-c:
Example Feynman diagrams depicting the simplified models used. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model. |
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Figure 1-d:
Example Feynman diagrams depicting the simplified models used. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model. |
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Figure 2:
The lost-lepton and τhad event yields as predicted directly from simulation in the signal regions, shown in red, and from the prediction procedure applied to simulated eγ or μγ events, shown in blue. The error bars correspond to the statistical uncertainties from the limited number of events in simulation. The bottom panel shows the ratio of the simulation expectation (Exp.) and the simulation-based prediction (Pred.). The hashed area shows the expected uncertainties from parton distribution functions, renormalization and factorization scale uncertainties, and data-to-simulation correction factor uncertainties. The categories, denoted by dashed lines, are labeled as Nbj, where j refers to the number of jets and b refers to the number of b-tagged jets. The numbered bins within each category are the various pTmiss bins. In each of these regions, the first bin corresponds to 100 <pTmiss< 200 GeV, which is used for SM predictions. Note that the kinematic variable requirements used to derive the average transfer factors are different from those used to define the search regions. Expectations and predictions are compatible within uncertainties. |
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Figure 3:
Validation of the double ratio κ in each Njets−Nb-jets region for zero photon events. The black points are the observed κ values after subtracting the electroweak contamination based on the simulation. The blue points are the κ values computed directly from the simulation. The ratio is shown in the bottom panel, where the hashed region corresponds to the systematic uncertainty in the γ+jets prediction. In the label Nbj, j refers to the number of jets and b refers to the number of b-tagged jets. |
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Figure 4:
Distribution of predicted SM background events from various sources and observed events in each of the 25 signal regions. The categories, denoted by dashed lines, are labeled as Nbj, where j refers to the number of jets and b refers to the number of b-tagged jets. The numbered bins within each category are the various pTmiss bins. The lower pane shows the ratio of observed events to predicted SM background events. The error bars in the lower pane are the quadrature sum of the statistical uncertainty in the observed data and the systematic uncertainty in the predicted backgrounds before adjustments based on a maximum likelihood fit to data assuming a signal strength of zero. The observed event yields are consistent with the predicted SM backgrounds within one standard deviation in all bins except bin 2, as discussed in the text. |
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Figure 5:
Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis. |
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Figure 5-a:
Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis. |
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Figure 5-b:
Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis. |
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Figure 5-c:
Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis. |
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Figure 5-d:
Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis. |
Tables | |
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Table 1:
Predicted and observed event yields for each signal region. |
Summary |
A search for gluino and top squark pair production is presented, based on proton-proton collisions dataset with a center-of-mass energy of 13 TeV recorded in 2016 with the CMS detector. The data correspond to an integrated luminosity of 35.9 fb−1. Events are required to have at least one isolated photon with pT> 100 GeV, two jets with pT> 30 GeV and |η|<2.4, and large missing transverse momentum pmissT> 200 GeV. The data are categorized into 25 independent signal regions based on the number of jets, the number of b-tagged jets, and pmissT. Background yields from standard model processes are predicted using simulation and data control regions. The observed event yields are found to be consistent with expectations from the SM processes within uncertainties. Results are interpreted in the context of simplified models. Four such models are studied, three of which involve gluino pair production and one of which involves top squark pair production. All models assume a gauge-mediated supersymmetry breaking scenario, in which the lightest supersymmetric particle is a gravitino. We consider scenarios in which the gluino decays to a neutralino ˜χ01 and a pair of light-flavor quarks (T5qqqqHG), bottom quarks (T5bbbbZG), or top quarks (T5ttttZG). In the T5qqqqHG model, the ˜χ01 decays either to a photon and gravitino ˜G or to a Higgs boson and ˜G, with branching fraction 50%. In the T5bbbbZG and T5ttttZG models, the ˜χ01 decays either to a photon and ˜G or to a Z boson and ˜G, with branching fraction 50%. In the top squark pair production model (T6ttZG), top squarks decay to a top quark and ˜χ01, and the ˜χ01 decays to a photon and ˜G or to a Z boson and ˜G with a branching fraction of 50%. Using the next-to-leading-order plus next-to-leading-logarithmic cross sections for supersymmetric pair production, we place 95% confidence level upper limits on the gluino mass as large as 2120 GeV, depending on the model and m˜χ01, and limits on the top squark mass as large as 1230 GeV, depending on m˜χ01. These results improve upon those from previous searches for supersymmetry with photons [26,27]. |
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Compact Muon Solenoid LHC, CERN |
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