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CMS-SUS-17-010 ; CERN-EP-2018-186

Searches for pair production of charginos and top squarks in final states with two oppositely charged leptons in proton-proton collisions at $\sqrt{s} = $ 13 TeV

CMS Collaboration

20 July 2018

JHEP 11 (2018) 079

Abstract: A search for pair production of supersymmetric particles in events with two oppositely charged leptons (electrons or muons) and missing transverse momentum is reported. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected with the CMS detector during the 2016 data taking period at the LHC. No significant deviation is observed from the predicted standard model background. The results are interpreted in terms of several simplified models for chargino and top squark pair production, assuming $R$-parity conservation and with the neutralino as the lightest supersymmetric particle. When the chargino is assumed to undergo a cascade decay through sleptons, with a slepton mass equal to the average of the chargino and neutralino masses, exclusion limits at 95% confidence level are set on the masses of the chargino and neutralino up to 800 and 320 GeV, respectively. For the top squark pair production, the search focuses on models with a small mass difference between the top squark and the lightest neutralino. When the top squark decays into an off-shell top quark and a neutralino, the limits extend up to 420 and 360 GeV for the top squark and neutralino masses, respectively.

Links: e-print arXiv:1807.07799 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

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: Simplified-models diagrams of the chargino pair production with two benchmark decay modes: the left plot shows decays through intermediate sleptons or sneutrinos, while the right one displays prompt decays into a W boson and the lightest neutralino.
png pdf	Figure 1-a: Simplified-model diagram of the chargino pair production with decays through intermediate sleptons or sneutrinos.
png pdf	Figure 1-b: Simplified-model diagram of the chargino pair production with prompt decays into a W boson and the lightest neutralino.
png pdf	Figure 2: Simplified-models diagrams of the top squark pair production with two benchmark decay modes of the top squark: the left plot shows decays into a top quark and the lightest neutralino, while the right one displays prompt decays into a bottom quark and a chargino, further decaying into a neutralino and a W boson.
png pdf	Figure 2-a: Simplified-model diagram of the top squark pair production with top squark decays into a top quark and the lightest neutralino.
png pdf	Figure 2-b: Simplified-model diagram of the top squark pair production with top squark prompt decays into a bottom quark and a chargino, further decaying into a neutralino and a W boson.
png pdf	Figure 3: Observed and SM expected distributions of some observables used to define the SRs for events with two OC isolated leptons and $ {{p_{\mathrm {T}}} ^\text {miss}} \geq $ 140 GeV. Clockwise from top left: ${{p_{\mathrm {T}}} ^\text {miss}}$, ${{m_\mathrm {T2}} (\ell \ell)}$, ${\Delta \phi}$ between the ${\vec{p}}_{\mathrm {T}}^{\,\text {miss}} $ and the leading jet (required not to be b-tagged and with $ {p_{\mathrm {T}}} > $ 150 GeV, events missing this requirements are shown in the first bin), and multiplicity of b-tagged jets in the event. The last bin includes the overflow entries. In the bottom panel, the ratio of observed and expected yields is shown. The hatched band represents the total uncertainty in the background expectation, as described in Section 7.
png pdf	Figure 3-a: Observed and SM expected distributions of ${{p_{\mathrm {T}}} ^\text {miss}}$, one of the observables used to define the SRs for events with two OC isolated leptons and $ {{p_{\mathrm {T}}} ^\text {miss}} \geq $ 140 GeV. The last bin includes the overflow entries. In the bottom panel, the ratio of observed and expected yields is shown. The hatched band represents the total uncertainty in the background expectation, as described in Section 7.
png pdf	Figure 3-b: Observed and SM expected distributions of ${{m_\mathrm {T2}} (\ell \ell)}$, one of the observables used to define the SRs for events with two OC isolated leptons and $ {{p_{\mathrm {T}}} ^\text {miss}} \geq $ 140 GeV. The last bin includes the overflow entries. In the bottom panel, the ratio of observed and expected yields is shown. The hatched band represents the total uncertainty in the background expectation, as described in Section 7.
png pdf	Figure 3-c: Observed and SM expected distributions of the multiplicity of b-tagged jets in the event, one of the observables used to define the SRs for events with two OC isolated leptons and $ {{p_{\mathrm {T}}} ^\text {miss}} \geq $ 140 GeV. The last bin includes the overflow entries. In the bottom panel, the ratio of observed and expected yields is shown. The hatched band represents the total uncertainty in the background expectation, as described in Section 7.
png pdf	Figure 3-d: Observed and SM expected distributions of ${\Delta \phi}$ between the ${\vec{p}}_{\mathrm {T}}^{\,\text {miss}} $ and the leading jet (required not to be b-tagged and with $ {p_{\mathrm {T}}} > $ 150 GeV, events missing this requirements are shown in the first bin), one of the observables used to define the SRs for events with two OC isolated leptons and $ {{p_{\mathrm {T}}} ^\text {miss}} \geq $ 140 GeV. The last bin includes the overflow entries. In the bottom panel, the ratio of observed and expected yields is shown. The hatched band represents the total uncertainty in the background expectation, as described in Section 7.
png pdf	Figure 4: Distributions of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SRs with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV (upper plots), 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV (middle), and $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV (lower), for DF events without b-tagged jets and at least one jet (left plots) and no jets (right plots). The lower plot for the SR with $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV shows all the events without b-tagged jets regardless of their jet multiplicity. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 4-a: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SR with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV for DF events without b-tagged jets and at least one jet. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 4-b: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SR with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV for DF events with no jet. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 4-c: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SR with 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV for DF events without b-tagged jets and at least one jet. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 4-d: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SR with 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV for DF events with no jet. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 4-e: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the chargino SR with $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV for DF events without b-tagged jets regardless of their jet multiplicity. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for chargino pair production with $ {m_{\tilde{\chi}^\pm _{1}}} = $ 500 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 200 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 5: The same distributions of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4, but for SF events.
png pdf	Figure 5-a: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4-a, but for SF events.
png pdf	Figure 5-b: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4-b, but for SF events.
png pdf	Figure 5-c: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4-c, but for SF events.
png pdf	Figure 5-d: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4-d, but for SF events.
png pdf	Figure 5-e: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 4-e, but for SF events.
png pdf	Figure 6: Distributions of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SRs with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV (upper plots), 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV (middle), or $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV (lower), for DF events with b-tagged jets (left plots) and without b-tagged jets (right plots). The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-a: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV, for DF events with b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-b: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with 140 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV, for DF events without b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-c: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV, for DF events with b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-d: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with 200 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 300 GeV, for DF events without b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-e: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV, for DF events with b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 6-f: Distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ after the fit to data in the top squark SR with $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV, for DF events without b-tagged jets. The solid magenta histogram shows the expected ${{m_\mathrm {T2}} (\ell \ell)}$ distribution for top squark pair production with $ {m_{\tilde{\mathrm {t}}_1}} = $ 350 GeV and $ {m_{\tilde{\chi}^{0}_{1}}} = $ 225 GeV. Expected total SM contributions before the fit (dark blue dashed line) and after a background+signal fit (dark red dotted line) are also shown. The last bin includes the overflow entries. In the bottom panel, the ratio of data and SM expectations is shown for the expected total SM contribution after the fit using the background-only hypothesis (black dots) and before any fit (dark blue dashed line). The hatched band represents the total uncertainty after the fit.
png pdf	Figure 7: The same distributions of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6, but for SF events.
png pdf	Figure 7-a: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-a, but for SF events.
png pdf	Figure 7-b: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-b, but for SF events.
png pdf	Figure 7-c: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-c, but for SF events.
png pdf	Figure 7-d: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-d, but for SF events.
png pdf	Figure 7-e: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-e, but for SF events.
png pdf	Figure 7-f: The same distribution of ${{m_\mathrm {T2}} (\ell \ell)}$ as Fig. 6-f, but for SF events.
png pdf	Figure 8: Left: upper limits at 95% CL on the chargino pair production cross section as a function of the chargino and neutralino masses, when the chargino undergoes a cascade decay ${\tilde{\chi}^\pm _{1}} \to {\tilde{\ell}}\nu (\ell {\tilde{\nu}} ) \to \ell \nu \tilde{\chi}^{0}_{1}$. Exclusion regions in the plane (${m_{\tilde{\chi}^\pm _{1}}}$, ${m_{\tilde{\chi}^{0}_{1}}}$) are determined by comparing the upper limits with the NLO+NLL production cross sections. The thick dashed red line shows the expected exclusion region. The thin dashed red lines show the variation of the exclusion regions due to the experimental uncertainties. The thick black line shows the observed exclusion region, while the thin black lines show the variation of the exclusion regions due to the theoretical uncertainties in the production cross section. Right: observed and expected upper limits at 95% CL as a function of the chargino mass for a neutralino mass of 1 GeV, assuming chargino decays into a neutralino and a W boson ($ \tilde{\chi}^\pm _{1} \to {\mathrm {W}} \tilde{\chi}^{0}_{1} $).
png pdf root	Figure 8-a: Upper limits at 95% CL on the chargino pair production cross section as a function of the chargino and neutralino masses, when the chargino undergoes a cascade decay ${\tilde{\chi}^\pm _{1}} \to {\tilde{\ell}}\nu (\ell {\tilde{\nu}} ) \to \ell \nu \tilde{\chi}^{0}_{1}$. Exclusion regions in the plane (${m_{\tilde{\chi}^\pm _{1}}}$, ${m_{\tilde{\chi}^{0}_{1}}}$) are determined by comparing the upper limits with the NLO+NLL production cross sections. The thick dashed red line shows the expected exclusion region. The thin dashed red lines show the variation of the exclusion regions due to the experimental uncertainties. The thick black line shows the observed exclusion region, while the thin black lines show the variation of the exclusion regions due to the theoretical uncertainties in the production cross section.
png pdf root	Figure 8-b: Observed and expected upper limits at 95% CL as a function of the chargino mass for a neutralino mass of 1 GeV, assuming chargino decays into a neutralino and a W boson ($ \tilde{\chi}^\pm _{1} \to {\mathrm {W}} \tilde{\chi}^{0}_{1} $).
png pdf	Figure 9: Upper limits at 95% CL on the top squark production cross section as a function of the top squark and neutralino masses. The plot on the left shows the results when top squark decays into a top quark and a neutralino are assumed. The two diagonal gray dashed lines enclose the compressed region where $ {m_{{\mathrm {W}}}} < {m_{\tilde{\mathrm {t}}_1}} - {m_{\tilde{\chi}^{0}_{1}}} < {m_{{\mathrm {t}}}} $. The plot on the right gives the limits for top squarks decaying into a bottom quark and a chargino, with the latter successively decaying into a W boson and a neutralino. The mass of the chargino is assumed to be equal to the average of the top squark and neutralino masses. Exclusion regions in the plane (${m_{\tilde{\mathrm {t}}_1}}$, ${m_{\tilde{\chi}^{0}_{1}}}$) are determined by comparing the upper limits with the NLO+NLL production cross sections. The thick dashed red line shows the expected exclusion region. The thin dashed red lines show the variation of the exclusion regions due to the experimental uncertainties. The thick black line shows the observed exclusion region, while the thin black lines show the variation of the exclusion regions due to the theoretical uncertainties in the production cross section.
png pdf root	Figure 9-a: Upper limits at 95% CL on the top squark production cross section as a function of the top squark and neutralino masses. The plot shows the results when top squark decays into a top quark and a neutralino are assumed. The two diagonal gray dashed lines enclose the compressed region where $ {m_{{\mathrm {W}}}} < {m_{\tilde{\mathrm {t}}_1}} - {m_{\tilde{\chi}^{0}_{1}}} < {m_{{\mathrm {t}}}} $. Exclusion regions in the plane (${m_{\tilde{\mathrm {t}}_1}}$, ${m_{\tilde{\chi}^{0}_{1}}}$) are determined by comparing the upper limits with the NLO+NLL production cross sections. The thick dashed red line shows the expected exclusion region. The thin dashed red lines show the variation of the exclusion regions due to the experimental uncertainties. The thick black line shows the observed exclusion region, while the thin black lines show the variation of the exclusion regions due to the theoretical uncertainties in the production cross section.
png pdf root	Figure 9-b: Upper limits at 95% CL on the top squark production cross section as a function of the top squark and neutralino masses. The plot gives the limits for top squarks decaying into a bottom quark and a chargino, with the latter successively decaying into a W boson and a neutralino. The mass of the chargino is assumed to be equal to the average of the top squark and neutralino masses. Exclusion regions in the plane (${m_{\tilde{\mathrm {t}}_1}}$, ${m_{\tilde{\chi}^{0}_{1}}}$) are determined by comparing the upper limits with the NLO+NLL production cross sections. The thick dashed red line shows the expected exclusion region. The thin dashed red lines show the variation of the exclusion regions due to the experimental uncertainties. The thick black line shows the observed exclusion region, while the thin black lines show the variation of the exclusion regions due to the theoretical uncertainties in the production cross section.

Tables
png pdf	Table 1: Definition of the baseline selection used in the searches for chargino and top squark pair production.
png pdf	Table 2: Definition of the SRs for the chargino search as a function of the ${{p_{\mathrm {T}}} ^\text {miss}} $ value, the b-jet multiplicity and jet multiplicity. Also shown are the CRs with b-tagged jets used for the normalization of the ${{\mathrm {t}\overline {\mathrm {t}}}}$ and ${{\mathrm {t}} {\mathrm {W}}}$ backgrounds. Each of the regions is further divided in seven ${{m_\mathrm {T2}} (\ell \ell)}$ bins as described in the last row.
png pdf	Table 3: Definition of the SRs for the top squark production search as a function of the ${{p_{\mathrm {T}}} ^\text {miss}} $ value, the b-jet multiplicity and the ISR jet requirement. Each of the regions is further divided in seven ${{m_\mathrm {T2}} (\ell \ell)}$ bins as described in the last row.
png pdf	Table 4: Summary of the normalization scale factors for ${{{\mathrm {t}\overline {\mathrm {t}}}} {\mathrm {Z}}}$, ${{\mathrm {W}} {\mathrm {Z}}}$, and ${{\mathrm {Z}} {\mathrm {Z}}}$ backgrounds in the SRs used for the chargino (a) and top squark (b) searches. Uncertainties include the statistical uncertainties of data and simulated event samples, and the systematic uncertainties in the purity of the CRs.
png pdf	Table 5: Sizes of systematic uncertainties in the predicted yields for SM processes. The first column shows the range of the uncertainties in the global background normalization across the different SRs. The second column quantifies the effect on the ${{m_\mathrm {T2}} (\ell \ell)}$ shape. This is computed by taking the maximum variation across the ${{m_\mathrm {T2}} (\ell \ell)}$ bins (after renormalizing for the global change of all the distribution) in each SR. The range of this variation across the SRs is given.
png pdf	Table 6: Same as in Table 5 for two representative signal points, one for chargino pair production and one for top squark pair production.
png pdf	Table 7: Observed and expected yields of DF (the upper half of Table) and SF (the lower half) events in the SRs for the chargino search. The quoted uncertainties in the background predictions include statistical and systematic contributions.
png pdf	Table 8: Observed and expected yields of DF (the upper half of Table) and SF (the lower half) events in the SRs for the top squark search. The quoted uncertainties in the background predictions include statistical and systematic contributions.

Summary

A search has been presented for pair production of supersymmetric particles in events with two oppositely charged isolated leptons and missing transverse momentum. The data used consist of a sample of proton-proton collisions collected with the CMS detector during the 2016 LHC run at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No evidence for a deviation with respect to standard model predictions was observed in data. The results have been interpreted as upper limits on the cross sections of supersymmetric particle production for several simplified model spectra. Chargino pair production has been investigated in two possible decay modes. If the chargino is assumed to undergo a cascade decay through sleptons, an exclusion region in the ($m_{\tilde{\chi}^{\pm}_1}$, $m_{\tilde{\chi}^0_1}$) plane can be derived, extending to chargino masses of 800 GeV and neutralino masses of 320 GeV. These are the most stringent limits on this model to date. For chargino decays into a neutralino and a W boson, limits on the production cross section have been derived assuming a neutralino mass of 1 GeV, and chargino masses in the range 170-200 GeV have been excluded. Top squark pair production was also tested, with a focus on compressed decay modes. A model with the top squark decaying into a top quark and a neutralino was considered. In the region where $m_{\mathrm{W}} < m_{\tilde{\mathrm{t}}_{1}}-m_{\tilde{\chi}^0_1} < m_{\mathrm{t}}$, limits extend up to 420 and 360 GeV for the top squark and neutralino masses, respectively. An alternative model has also been considered, where the top squark decays into a chargino and a bottom quark, with the chargino subsequently decaying into a W boson and the lightest neutralino. The mass of the chargino is assumed to be average between the top squark and neutralino masses, which gives a lower bound to the mass difference (${\Delta m} $) between the top squark and the neutralino of ${\Delta m} \approx 2\,m_{\mathrm{W}}$. This search reduces by about 50 GeV the minimum ${\Delta m}$ excluded in the previous result with two leptons in the final state [30] from the CMS Collaboration, excluding top squark masses in the range 225-325 GeV for ${\Delta m} \approx 2\,m_{\mathrm{W}}$. In summary, by exploiting the full data set collected by the CMS experiment in 2016, this search extends the existing exclusion limits on the pair production of charginos decaying via sleptons [29], improving by about 70 GeV the limit on the chargino mass for a massless neutralino. Exclusion limits on the top squark pair production extend the results obtained by the CMS Collaboration in final states with two oppositely charged leptons [30] to the compressed region, where they are competitive with the results obtained by the ATLAS Collaboration in the same decay channel [35].

Additional Figures
png pdf root	Additional Figure 1: Correlation matrix for the background between the signal regions used in the chargino pair production search.
png pdf root	Additional Figure 2: Covariance matrix for the background between the signal regions used in the chargino pair production search.
png pdf root	Additional Figure 3: Correlation matrix for the background between the signal regions used in the top squark pair production search.
png pdf root	Additional Figure 4: Covariance matrix for the background between the signal regions used in the top squark pair production search.

Additional Tables
png pdf	Additional Table 1: Expected signal yields at different stages of the baseline event selection for two representative signal points, one for chargino pair production and one for top squark pair production. The yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$.
png pdf	Additional Table 2: Expected yields of DF (the upper half of Table) and SF (the lower half) events in the signal regions used in the chargino search, for a reference ${{\tilde{\chi}^\pm _{1}} \to {\tilde{\ell}}\nu \text (\ell {\tilde{\nu}} \text )\to \ell \nu {\tilde{\chi}^{0}_{1}}}$ signal with $ {m_{{\tilde{\chi}^\pm _{1}}}} = $ 500 GeV and $ {m_{{\tilde{\chi}^{0}_{1}}}} = $ 200 GeV. The yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. Quoted uncertainties are statistical only.
png pdf	Additional Table 3: Expected yields of DF (the upper half of Table) and SF (the lower half) events in the signal regions used in the top squark search, for a reference $ {\tilde{\mathrm {t}}_1} \to {\mathrm {t}} {\tilde{\chi}^{0}_{1}} $ signal with $ {m_{{\tilde{\mathrm {t}}_1}}} = $ 350 GeV and $ {m_{{\tilde{\chi}^{0}_{1}}}} = $ 225 GeV. The yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. Quoted uncertainties are statistical only.

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