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| CMS-SUS-20-001 ; CERN-EP-2020-231 | ||
| Search for supersymmetry in final states with two oppositely charged same-flavor leptons and missing transverse momentum in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 15 December 2020 | ||
| JHEP 04 (2021) 123 | ||
| Abstract: A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass; a kinematic edge in the invariant mass distribution of the lepton pair; and the nonresonant production of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1875 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios. | ||
| Links: e-print arXiv:2012.08600 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures & Tables | References | CMS Publications |
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| Figures | |
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Figure 1:
Diagrams for models of neutralino/chargino production (upper left), GMSB neutralino pair production with ZZ (upper right) and ZH bosons (lower left) in the final state, and direct slepton pair production (lower right). In the first GMSB neutralino pair production model, the $\tilde{\chi}^0_1$ is assumed to decay exclusively into a Z boson, while in the latter, the ZH final state is accompanied by the ZZ final state with 50% branching fractions of the $\tilde{\chi}^0_1$ decaying into an H or a Z boson. Only ZH and ZZ final states are taken into account in the analysis, since the contribution of the HH topology to our signal regions is expected to be negligible. Such models predict the SUSY particles to be produced via EW interactions, with limited if any production of accompanying quarks in the final state. |
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Figure 1-a:
Diagram for neutralino/chargino production. The model predicts the SUSY particles to be produced via EW interactions, with limited if any production of accompanying quarks in the final state. |
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Figure 1-b:
Diagram for GMSB neutralino pair production with ZZ bosons in the final state. The $\tilde{\chi}^0_1$ is assumed to decay exclusively into a Z boson. The model predicts the SUSY particles to be produced via EW interactions, with limited if any production of accompanying quarks in the final state. |
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Figure 1-c:
Diagram for GMSB neutralino pair production with ZH bosons in the final state. The ZH final state is accompanied by the ZZ final state with 50% branching fractions of the $\tilde{\chi}^0_1$ decaying into an H or a Z boson. Only ZH and ZZ final states are taken into account in the analysis, since the contribution of the HH topology to our signal regions is expected to be negligible. The model predicts the SUSY particles to be produced via EW interactions, with limited if any production of accompanying quarks in the final state. |
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Figure 1-d:
Diagram for direct slepton pair production. The model predicts the SUSY particles to be produced via EW interactions, with limited if any production of accompanying quarks in the final state. |
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Figure 2:
Diagram for GMSB gluino (${\mathrm{\tilde{g}}}$) pair production (left), where each ${\mathrm{\tilde{g}}}$ decays into a pair of quarks and a neutralino. The neutralino then decays to a Z boson and an LSP. Diagrams for sbottom $\tilde{\mathrm{b}}$ (center) and squark $\tilde{\mathrm{q}}$ (right) pair production are also shown. Such models feature a mass edge from the decay of a $\tilde{\chi}^0_2$ via an intermediate slepton, $\tilde{\ell}$. In the central diagram, a pair of b quarks is present in the final state. In these models we assume a fixed $\tilde{\chi}^0_1$ mass of 100 GeV, while the mass of the slepton is taken to be equidistant from the masses of the two neutralinos. Only the lightest $\tilde{\mathrm{b}}$ mass eigenstate, $\tilde{\mathrm{b}} _1$, is assumed to be involved in the models considered. All these models assume strong production of SUSY particles and predict an abundance of quarks in the final state. |
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Figure 2-a:
Diagram for GMSB gluino (${\mathrm{\tilde{g}}}$) pair production, where each ${\mathrm{\tilde{g}}}$ decays into a pair of quarks and a neutralino. The neutralino then decays to a Z boson and an LSP. |
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Figure 2-b:
Diagram for sbottom $\tilde{\mathrm{b}}$ pair production. Only the lightest $\tilde{\mathrm{b}}$ mass eigenstate, $\tilde{\mathrm{b}} _1$, is assumed to be involved. A pair of b quarks is present in the final state. Such model features a mass edge from the decay of a $\tilde{\chi}^0_2$ via an intermediate slepton, $\tilde{\ell}$. We assume a fixed $\tilde{\chi}^0_1$ mass of 100 GeV, while the mass of the slepton is taken to be equidistant from the masses of the two neutralinos. The model assumes strong production of SUSY particles and predicts an abundance of quarks in the final state. |
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Figure 2-c:
Diagram for squark $\tilde{\mathrm{q}}$ pair production. Such model features a mass edge from the decay of a $\tilde{\chi}^0_2$ via an intermediate slepton, $\tilde{\ell}$. We assume a fixed $\tilde{\chi}^0_1$ mass of 100 GeV, while the mass of the slepton is taken to be equidistant from the masses of the two neutralinos. The model assumes strong production of SUSY particles and predicts an abundance of quarks in the final state. |
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Figure 3:
Distributions in ${m_{\ell \ell}}$ (upper left), ${{p_{\mathrm {T}}} ^\text {miss}}$ (upper right), and $ {p_{\mathrm {T}}} ^{\ell \ell}$ (lower) in a ${\mathrm{t} {}\mathrm{\bar{t}}} $-enriched CR in data. The flavor-symmetric background prediction obtained from data, as discussed in the main text, (gray solid histogram) is compared to data (black markers). Other backgrounds are estimated directly from simulation (green and blue solid histograms). The uncertainty band includes both the statistical and systematic contributions to the prediction. The last bin includes overflow events. |
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Figure 3-a:
Distribution in ${m_{\ell \ell}}$ in a ${\mathrm{t} {}\mathrm{\bar{t}}} $-enriched CR in data. The flavor-symmetric background prediction obtained from data, as discussed in the main text, (gray solid histogram) is compared to data (black markers). Other backgrounds are estimated directly from simulation (green and blue solid histograms). The uncertainty band includes both the statistical and systematic contributions to the prediction. The last bin includes overflow events. |
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Figure 3-b:
Distribution in ${{p_{\mathrm {T}}} ^\text {miss}}$ in a ${\mathrm{t} {}\mathrm{\bar{t}}} $-enriched CR in data. The flavor-symmetric background prediction obtained from data, as discussed in the main text, (gray solid histogram) is compared to data (black markers). Other backgrounds are estimated directly from simulation (green and blue solid histograms). The uncertainty band includes both the statistical and systematic contributions to the prediction. The last bin includes overflow events. |
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Figure 3-c:
Distribution in $ {p_{\mathrm {T}}} ^{\ell \ell}$ in a ${\mathrm{t} {}\mathrm{\bar{t}}} $-enriched CR in data. The flavor-symmetric background prediction obtained from data, as discussed in the main text, (gray solid histogram) is compared to data (black markers). Other backgrounds are estimated directly from simulation (green and blue solid histograms). The uncertainty band includes both the statistical and systematic contributions to the prediction. The last bin includes overflow events. |
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Figure 4:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the on-Z VRs. Comparison in the strong on-Z VRs associated to (upper left) SRA, (upper right) SRB, and (middle left) SRC. Comparison in the EW on-Z VRs: (middle right) boosted VZ, (lower left) resolved VZ, and (lower right) HZ. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-a:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the strong on-Z VRs associated to SRA. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-b:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the strong on-Z VRs associated to SRB. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-c:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the strong on-Z VRs associated to SRC. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-d:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the EW on-Z VRs associated to boosted VZ. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-e:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the EW on-Z VRs associated to resolved VZ. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 4-f:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution observed in data (black markers) is compared to the background prediction (solid histograms) in the EW on-Z VRs associated to HZ. The uncertainty band includes both the systematic and statistical components of the uncertainty in the prediction. The last bin includes overflow events. |
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Figure 5:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z (upper) SRA, (middle) SRB, and (lower) SRC regions for (left) the b veto and (right) b tag categories before the fits to data discussed in Section 8. The lower panel of each plot shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-a:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRA region for the b veto category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-b:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRA region for the b tag category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-c:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRB region for the b veto category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-d:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRB region for the b tag category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-e:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRC region for the b veto category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 5-f:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the strong-production on-Z SRC region for the b tag category before the fits to data discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each bin of ${{p_{\mathrm {T}}} ^\text {miss}}$. The hashed band in the upper panels shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distributions correspond to the gluino pair production model with the gluino ($\tilde{\chi}^0_1$) having a mass of 1600 (700) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 6:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the EW-production on-Z (upper left) boosted VZ, (upper right) resolved VZ, and (lower) HZ search regions before the fits to data described in Section 8. The lower panel of each figure shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for the boosted and resolved VZ search regions correspond to the $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_2$ production model with a $\tilde{\chi}^{\pm}_1 /\tilde{\chi}^0_2$ ($\tilde{\chi}^0_1$) mass of 400 (200) GeV,while for the HZ search region the ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to a $\tilde{\chi}^0_1$ pair production model decaying into a Higgs boson, a Z boson and two $\tilde{\mathrm{G}}$ with the $\tilde{\chi}^0_1$ ($\tilde{\mathrm{G}}$) having a mass of 500 (1) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 6-a:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the EW-production on-Z boosted VZ search region before the fits to data described in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for the boosted and resolved VZ search regions correspond to the $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_2$ production model with a $\tilde{\chi}^{\pm}_1 /\tilde{\chi}^0_2$ ($\tilde{\chi}^0_1$) mass of 400 (200) GeV,while for the HZ search region the ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to a $\tilde{\chi}^0_1$ pair production model decaying into a Higgs boson, a Z boson and two $\tilde{\mathrm{G}}$ with the $\tilde{\chi}^0_1$ ($\tilde{\mathrm{G}}$) having a mass of 500 (1) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 6-b:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the EW-production on-Z resolved VZ search region before the fits to data described in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for the boosted and resolved VZ search regions correspond to the $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_2$ production model with a $\tilde{\chi}^{\pm}_1 /\tilde{\chi}^0_2$ ($\tilde{\chi}^0_1$) mass of 400 (200) GeV,while for the HZ search region the ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to a $\tilde{\chi}^0_1$ pair production model decaying into a Higgs boson, a Z boson and two $\tilde{\mathrm{G}}$ with the $\tilde{\chi}^0_1$ ($\tilde{\mathrm{G}}$) having a mass of 500 (1) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 6-c:
The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution in data is compared to the SM background prediction in the EW-production on-Z HZ search region before the fits to data described in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for the boosted and resolved VZ search regions correspond to the $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_2$ production model with a $\tilde{\chi}^{\pm}_1 /\tilde{\chi}^0_2$ ($\tilde{\chi}^0_1$) mass of 400 (200) GeV,while for the HZ search region the ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to a $\tilde{\chi}^0_1$ pair production model decaying into a Higgs boson, a Z boson and two $\tilde{\mathrm{G}}$ with the $\tilde{\chi}^0_1$ ($\tilde{\mathrm{G}}$) having a mass of 500 (1) GeV. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each search region is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. The last bin includes overflow events. |
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Figure 7:
Results of the counting experiment in the edge search regions before the fits to data described in Section 8. In each search region, the number of observed events in data (black markers) is compared to the SM background prediction for the (left) b veto and (right) b tag categories. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal distribution corresponds to the $\tilde{\mathrm{b}}$ pair production model with the $\tilde{\mathrm{b}}$ ($\tilde{\chi}^0_2$) having a mass of 1250 (400) GeV. |
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Figure 7-a:
Results of the counting experiment in the edge search regions before the fits to data described in Section 8. In each search region, the number of observed events in data (black markers) is compared to the SM background prediction for the b veto category. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal distribution corresponds to the $\tilde{\mathrm{b}}$ pair production model with the $\tilde{\mathrm{b}}$ ($\tilde{\chi}^0_2$) having a mass of 1250 (400) GeV. |
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Figure 7-b:
Results of the counting experiment in the edge search regions before the fits to data described in Section 8. In each search region, the number of observed events in data (black markers) is compared to the SM background prediction for the b tag category. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal distribution corresponds to the $\tilde{\mathrm{b}}$ pair production model with the $\tilde{\mathrm{b}}$ ($\tilde{\chi}^0_2$) having a mass of 1250 (400) GeV. |
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Figure 8:
Fit the ${m_{\ell \ell}}$ distributions in data in the edge fit search regions under the signal+background hypothesis projected onto the (left) SF and (right) DF data samples. The fit shape is shown as a solid blue line. The individual fit components are indicated by the dashed and dotted lines. The flavor-symmetric background is shown as the black dashed line. The $\mathrm{Z} /\gamma ^*$+X background is displayed as the red dotted line. The extracted signal component is displayed as the purple dash-dotted line. The lower panel in each plot shows the difference between the observed data yield and the fit divided by the square root of the number of fitted events. |
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Figure 8-a:
Fit the ${m_{\ell \ell}}$ distributions in data in the edge fit search regions under the signal+background hypothesis projected onto the SF data sample. The fit shape is shown as a solid blue line. The individual fit components are indicated by the dashed and dotted lines. The flavor-symmetric background is shown as the black dashed line. The $\mathrm{Z} /\gamma ^*$+X background is displayed as the red dotted line. The extracted signal component is displayed as the purple dash-dotted line. The lower panel shows the difference between the observed data yield and the fit divided by the square root of the number of fitted events. |
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Figure 8-b:
Fit the ${m_{\ell \ell}}$ distribution in data in the edge fit search regions under the signal+background hypothesis projected onto the DF data sample. The fit shape is shown as a solid blue line. The lower panel shows the difference between the observed data yield and the fit divided by the square root of the number of fitted events. |
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Figure 9:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for events in the slepton (left) search regions and (right) control regions obtained by inverting the ${m_{\ell \ell}}$ selection used to obtain the DY background normalization for regions (upper) without jets and (lower) with jets. A background-only fit to data in the control region has been performed to determine the DY+jets contribution as discussed in Section 8. The lower panel of each plot shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to the direct slepton pair production model with a slepton mass of 600 GeV and a massless $\tilde{\chi}^0_1$ particle. The last bin includes overflow events. |
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Figure 9-a:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for events in the slepton search region obtained by inverting the ${m_{\ell \ell}}$ selection used to obtain the DY background normalization for regions without jets. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to the direct slepton pair production model with a slepton mass of 600 GeV and a massless $\tilde{\chi}^0_1$ particle. The last bin includes overflow events. |
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Figure 9-b:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for events in the slepton control region obtained by inverting the ${m_{\ell \ell}}$ selection used to obtain the DY background normalization for regions without jets. A background-only fit to data in the control region has been performed to determine the DY+jets contribution as discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The last bin includes overflow events. |
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Figure 9-c:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for events in the slepton search region obtained by inverting the ${m_{\ell \ell}}$ selection used to obtain the DY background normalization for regions with jets. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The signal ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution corresponds to the direct slepton pair production model with a slepton mass of 600 GeV and a massless $\tilde{\chi}^0_1$ particle. The last bin includes overflow events. |
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Figure 9-d:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for events in the slepton control region obtained by inverting the ${m_{\ell \ell}}$ selection used to obtain the DY background normalization for regions with jets. A background-only fit to data in the control region has been performed to determine the DY+jets contribution as discussed in Section 8. The lower panel shows the ratio of observed data to the SM prediction in each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. The hashed band shows the total uncertainty in the background prediction including statistical and systematic sources. The last bin includes overflow events. |
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Figure 10:
Cross section upper limits and exclusion contours at 95% CL for an SMS model of GMSB gluino pair production, as a function of the ${\mathrm{\tilde{g}}}$ and $\tilde{\chi}^0_1$ masses, obtained from the results in the strong-production on-Z search regions. The area enclosed by the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties on the signal cross section. |
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Figure 11:
Cross section upper limits and exclusion contours at 95% CL for an SMS model of $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_2$ production, with signatures containing a W and a Z bosons, as a function of the $\tilde{\chi}^{\pm}_1 /\tilde{\chi}^0_2$ and $\tilde{\chi}^0_1$ masses, obtained from the results in the EW-production on-Z search regions. The area enclosed by the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties on the signal cross section. |
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Figure 12:
Production cross section upper limits at 95% CL as a function of the $\tilde{\chi}^0_1$ mass, for a model of EW $\tilde{\chi}^0_1$ pair production, where either (left) both $\tilde{\chi}^0_1$ decay into a Z boson with a 100% branching fraction ($\mathcal {B}$), or (right) each $\tilde{\chi}^0_1$ can decay to a Z or an H with equal probability. The model assumes the production of mass-degenerate neutralinos and charginos that decay into $\tilde{\chi}^0_1$ possibly emitting soft particles, labeled as $\mathrm{X} _{\text {soft}}$. The magenta curve shows the theoretical production cross section with its uncertainty. The solid (dashed) black line represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. |
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Figure 12-a:
Production cross section upper limit at 95% CL as a function of the $\tilde{\chi}^0_1$ mass, for a model of EW $\tilde{\chi}^0_1$ pair production, where both $\tilde{\chi}^0_1$ decay into a Z boson with a 100% branching fraction ($\mathcal {B}$). The model assumes the production of mass-degenerate neutralinos and charginos that decay into $\tilde{\chi}^0_1$ possibly emitting soft particles, labeled as $\mathrm{X} _{\text {soft}}$. The magenta curve shows the theoretical production cross section with its uncertainty. The solid (dashed) black line represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. |
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Figure 12-b:
Production cross section upper limit at 95% CL as a function of the $\tilde{\chi}^0_1$ mass, for a model of EW $\tilde{\chi}^0_1$ pair production, where each $\tilde{\chi}^0_1$ can decay to a Z or an H with equal probability. The model assumes the production of mass-degenerate neutralinos and charginos that decay into $\tilde{\chi}^0_1$ possibly emitting soft particles, labeled as $\mathrm{X} _{\text {soft}}$. The magenta curve shows the theoretical production cross section with its uncertainty. The solid (dashed) black line represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. |
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Figure 13:
Cross section upper limits and exclusion contours at 95% CL for SMS models of (left) bottom and (right) light-flavor squark pair production. In these models, each squark decays into a quark and a $\tilde{\chi}^0_2$, and the $\tilde{\chi}^0_2$ then decays via an intermediate slepton, forming a kinematic edge in the ${m_{\ell \ell}}$ distribution. The limits are obtained from the results in the edge search regions, and are shown as a function of the (left) $\tilde{\mathrm{b}}$ or (right) $\tilde{\mathrm{q}}$ and $\tilde{\chi}^0_2$ masses. The thick black curve represents the observed upper limit on the squark mass, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties on the signal cross section. |
png pdf root |
Figure 13-a:
Cross section upper limits and exclusion contours at 95% CL for SMS models of bottom squark pair production. In these models, each squark decays into a quark and a $\tilde{\chi}^0_2$, and the $\tilde{\chi}^0_2$ then decays via an intermediate slepton, forming a kinematic edge in the ${m_{\ell \ell}}$ distribution. The limits are obtained from the results in the edge search regions, and are shown as a function of the $\tilde{\mathrm{b}}$ and $\tilde{\chi}^0_2$ masses. The thick black curve represents the observed upper limit on the squark mass, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties on the signal cross section. |
png pdf root |
Figure 13-b:
Cross section upper limits and exclusion contours at 95% CL for SMS models of light-flavor squark pair production. In these models, each squark decays into a quark and a $\tilde{\chi}^0_2$, and the $\tilde{\chi}^0_2$ then decays via an intermediate slepton, forming a kinematic edge in the ${m_{\ell \ell}}$ distribution. The limits are obtained from the results in the edge search regions, and are shown as a function of the $\tilde{\mathrm{q}}$ and $\tilde{\chi}^0_2$ masses. The thick black curve represents the observed upper limit on the squark mass, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties on the signal cross section. |
png pdf root |
Figure 14:
Cross section upper limits and exclusion contours at 95% CL for an SMS model of slepton pair production, as a function of the slepton and $\tilde{\chi}^0_1$ masses, obtained from the results in the slepton search regions. The area enclosed by the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limits and their $ \pm $1 and $ \pm $2 s.d. ranges. The thin black lines show the effect of the theoretical uncertainties in the signal cross section. |
| Tables | |
png pdf |
Table 1:
Summary of search category selections. In regions with the additional lepton veto selection, events containing additional leptons or charged isolated tracks are rejected. All the regions besides the edge search samples implement a veto to an additional lepton. The numbers in the rightmost column represent the edges of the bins that define the signal regions. Events in the edge search sample are further categorized as ${\mathrm{t} {}\mathrm{\bar{t}}} $-like and non-${\mathrm{t} {}\mathrm{\bar{t}}} $-like as described in Section 4.2.1. |
png pdf |
Table 2:
Summary of the ${r_{\mu /\mathrm{e}}}$ parameters obtained by fitting the lepton ${p_{\mathrm {T}}}$ and $\eta $, in a DY-enriched control region, for different data taking years. Only statistical uncertainties are shown. |
png pdf |
Table 3:
Summary of the uncertainties in background estimations performed on data. |
png pdf |
Table 4:
Summary of systematic uncertainties in the predicted Z+$\nu$ background yields, together with their typical sizes across the SRs. |
png pdf |
Table 5:
Predicted and observed event yields in the strong-production on-Z search regions, for each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin as defined in Table 2 before the fits to data discussed in Section 8. Uncertainties include both statistical and systematic sources. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each SR is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. |
png pdf |
Table 6:
Predicted and observed event yields in the EW-production on-Z search regions, for each ${{p_{\mathrm {T}}} ^\text {miss}}$ \ bin as defined in Table 2 before the fits to data described in Section 8. Uncertainties include both statistical and systematic sources. The ${{p_{\mathrm {T}}} ^\text {miss}}$ template prediction in each SR is normalized to the first ${{p_{\mathrm {T}}} ^\text {miss}}$ bin of each distribution in data. |
png pdf |
Table 7:
Predicted and observed yields in each bin of the edge search counting experiment as defined in Table 2 before the fits to data described in Section 8. Uncertainties include statistical and systematic sources. |
png pdf |
Table 8:
Results of the ${m_{\ell \ell}}$ unbinned maximum likelihood fit to data in the edge fit search region as defined in Table 2. The fitted yields of the $\mathrm{Z} /\gamma ^*$+X and flavor-symmetric background components are tabulated together with the fitted value of ${R_{\mathrm {SF/DF}}}$. The fitted signal contribution and the corresponding edge position are also shown. The local and global signal significances are expressed in terms of s.d. The uncertainties include both statistical and systematic sources. |
png pdf |
Table 9:
Predicted and observed event yields in the slepton search and control regions. A background-only fit to observation in the CR is performed to determine the DY+jets contribution as described in Section 8. Uncertainties include both statistical and systematic sources. |
png pdf |
Table 10:
Summary of the systematic uncertainties in the signal yields together with their typical sizes across the search regions and the SMS models under consideration. |
| Summary |
| A search is presented for phenomena beyond the standard model in events with two oppositely charged same-flavor leptons and missing transverse momentum in the final state. The search is performed in a sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected with the CMS detector corresponding to an integrated luminosity of 137 fb$^{-1}$. Search regions are defined to be sensitive to a wide range of signatures. The observed event yields and distributions are found to be consistent with the expectations from the standard model. The results are used to set upper limits on the production cross sections of simplified models of supersymmetry. Gluino masses are excluded up to 1875 GeV, light-flavor (bottom) squark masses up to 1800 (1600) GeV, chargino (neutralino) masses up to 750 (800) GeV, and slepton masses up to 700 GeV, typically extending the reach over previous CMS results by a few hundred GeV. |
| Additional Figures | |
png pdf root |
Additional Figure 1:
Pre-fit background covariance matrix (left) and correlation matrix (right), for the slepton signal regions. |
png pdf root |
Additional Figure 2:
Pre-fit background covariance matrix for the edge signal regions. |
png pdf root |
Additional Figure 3:
Pre-fit background covariance matrix for the on-Z strong signal regions. |
png pdf root |
Additional Figure 4:
Pre-fit background covariance matrix for the on-Z electroweak signal regions. |
| Additional Tables | |
png pdf |
Additional Table 1:
Number of events slepton signal events selected after each selection criterion in the slepton signal regions for models assuming (middle column) $m_{{{\ell}}} = $ 600 GeV and $m_{\tilde{\chi}^{0}_{1}} = $ 0 GeV, and (right column) $m_{{{\ell}}} = $ 600 GeV and $m_{\tilde{\chi}^{0}_{1}} = $ 400 GeV, respectively. |
png pdf |
Additional Table 2:
Number of gluino production signal events selected after each selection criterion in the strong signal regions for models assuming (middle column) $m_{{\mathrm {\tilde{g}}}} = $ 1600 GeV, $m_{\tilde{\chi}^{0}_{1}} = $ 700 GeV and (right column) $m_{{\mathrm {\tilde{g}}}} = $ 2200 GeV, $m_{\tilde{\chi}^{0}_{1}} = $ 800 GeV |
png pdf |
Additional Table 3:
Number of chargino-neutralino signal events selected after each selection criterion in the strong signal regions for models assuming (middle column) $m_{{\tilde{\chi}^{0}_{2}}} = $ 400 GeV, $m_{\tilde{\chi}^{0}_{1}} = $ 50 GeV and (right column) $m_{{\tilde{\chi}^{0}_{2}}} = $ 800 GeV, $m_{\tilde{\chi}^{0}_{1}} = $ 200 GeV |
png pdf |
Additional Table 4:
Number of TChiZZ signal events selected after each selection criterion in the strong signal regions for models assuming (middle column) $m_{\tilde{\chi}^{0}_{1}} = $ 400 GeV and (right column) $m_{\tilde{\chi}^{0}_{1}} = $ 800 GeV |
png pdf |
Additional Table 5:
Number of HZ signal events (composite TChiHZ and TChiZZ with 50% branching fractions) selected after each selection criterion in the strong signal regions for models assuming (middle column) $m_{\tilde{\chi}^{0}_{1}} = $ 400 GeV and (right column) $m_{\tilde{\chi}^{0}_{1}} = $ 800 GeV |
png pdf |
Additional Table 6:
Number of sbottom edge signal events selected after each selection criterion in the edge signal regions for models assuming (middle column) $m_{{\tilde{\mathrm {b}}}}=1300, m_{{\tilde{\chi}^{0}_{2}}} = $ 400 GeV and (right column) $m_{{\tilde{\mathrm {b}}}}=$ 1500, $m_{{\tilde{\chi}^{0}_{2}}} = $ 1200 GeV. Total dilepton events refers to luminosity $\times $ cross section $\times $ branching ratio. The last two lines are exclusive to each other. |
png pdf |
Additional Table 7:
Number of light squark edge signal events selected after each selection criterion in the edge signal regions for models assuming (middle column) $m_{{\mathrm {\tilde{q}}}}=1600, m_{{\tilde{\chi}^{0}_{2}}} = $ 400 GeV and (right column) $m_{{\mathrm {\tilde{q}}}}=$ 1700, $m_{{\tilde{\chi}^{0}_{2}}} = $ 1200 GeV. Total dilepton events refers to luminosity $\times $ cross section $\times $ branching ratio. The last two lines are exclusive to each other. |
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