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| CMS-PAS-SUS-16-046 | ||
| Search for GMSB supersymmetry in events with at least one photon and missing transverse momentum in pp collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| March 2017 | ||
| Abstract: A search for supersymmetry with gauge-mediated supersymmetry breaking in electroweak and strong production and final states with photons and large missing transverse momentum is presented in this note. The data sample was collected in 2016 in pp collisions at $ \sqrt{s} = $ 13 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. Scenarios are studied, in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape undetected. The event selection was optimised for high sensitivity to both electroweak and strong production SUSY scenarios. No indication for the presence of new physics is observed. The analysis excludes gaugino masses below 750 GeV at the 95% confidence level in a simplified model with electroweak production of mass-degenerate charginos and neutralinos and sets stringent limits in four strong production simplified models based on gluino and squark pair-production. The analysis currently sets the most stringent limits in the electroweak model studied and in the compressed mass phase space of the strong production models. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PLB 780 (2018) 118. The superseded preliminary plots can be found here. |
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| Figures & Tables | Summary | Additional Figures & Tables | References | CMS Publications |
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Additional information on efficiencies needed for reinterpretation of these results are available here. Additional technical material for CMS speakers can be found here. |
| Figures | |
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Figure 1:
In the TChiWg scenario, the gauginos are mass-degenerate, and the $\tilde{ \chi }^0 _1$ decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $ and the chargino decays as $\tilde{ \chi }^{\pm} _1\to \mathrm {W}^{\pm }\tilde{ \mathrm{G} } $. |
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Figure 2:
For strong gluino pair-production the simplified scenarios T5gg (a) and T5Wg (b) and for squark pair-production the simplified scenarios T6gg (c) and T6Wg (d) are studied. The neutralino decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $, while the chargino decays as $\tilde{ \chi }^{\pm} _1\to \mathrm {W}^{\pm }\tilde{ \mathrm{G} } $. In the T5Wg and T6Wg scenario, a branching ratio of 50% is assumed for the decays $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^0 _1$, and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^0 _1$, respectively. |
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Figure 2-a:
For strong gluino pair-production the simplified scenario T5gg is studied. The neutralino decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $. |
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Figure 2-b:
For strong gluino pair-production the simplified scenario T5Wg is studied. The neutralino decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $, while the chargino decays as $\tilde{ \chi }^{\pm} _1\to \mathrm {W}^{\pm }\tilde{ \mathrm{G} } $. A branching ratio of 50% is assumed for the decays $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^0 _1$, and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^0 _1$, respectively. |
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Figure 2-c:
For squark pair-production the simplified scenario T6gg is studied. The neutralino decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $. |
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Figure 2-d:
For squark pair-production the simplified scenario T6Wg is studied. The neutralino decays as $\tilde{ \chi }^0 _1\to \gamma \tilde{ \mathrm{G} } $, while the chargino decays as $\tilde{ \chi }^{\pm} _1\to \mathrm {W}^{\pm }\tilde{ \mathrm{G} } $. A branching ratio of 50% is assumed for the decays $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {g}}\rightarrow \mathrm{qq}\tilde{ \chi }^0 _1$, and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^{\pm} _1$ and $\tilde{\text {q}}\rightarrow \mathrm{q}\tilde{ \chi }^0 _1$, respectively. |
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Figure 3:
Template fit result. The post-fit distributions for $\gamma $+jets (blue) and V(+$\gamma $) (orange) together with the fixed background (magenta) and the total fit distribution stacked onto the fixed backgrounds (red) are shown. The statistical uncertainty of the post-fit distribution is shown in the red hatched area and the systematic uncertainty of the fixed background is indicated with the magenta hatched area. The values in the legend are the resulting scale factors. The pull distribution only considers the statistical uncertainty. Systematic uncertainties are not included and especially cover the deviations for low and high values of ${\Delta \phi ( p_{\mathrm{T}}^{\text{miss}} ,\text {nearest jet}/\gamma )} $. |
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Figure 4:
Validation of the electron misidentification background estimation method using MC simulation. In the selection with at least one photon with $ {p_{\mathrm {T}}} > $ 100 GeV the $\text {e}\to \gamma $ estimation method is compared to direct simulation in the photon transverse momentum (a) and the $p_{\mathrm{T}}^{\text{miss}}$ distribution (b). Events populating the phase space beyond the shown range are included in the last bin. The bin contents are divided by the bin widths. |
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Figure 4-a:
Validation of the electron misidentification background estimation method using MC simulation. In the selection with at least one photon with $ {p_{\mathrm {T}}} > $ 100 GeV the $\text {e}\to \gamma $ estimation method is compared to direct simulation in the photon transverse momentum distribution. Events populating the phase space beyond the shown range are included in the last bin. The bin contents are divided by the bin widths. |
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Figure 4-b:
Validation of the electron misidentification background estimation method using MC simulation. In the selection with at least one photon with $ {p_{\mathrm {T}}} > $ 100 GeV the $\text {e}\to \gamma $ estimation method is compared to direct simulation in the $p_{\mathrm{T}}^{\text{miss}}$ distribution. Events populating the phase space beyond the shown range are included in the last bin. The bin contents are divided by the bin widths. |
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Figure 5:
Data to simulation comparisons in the control region (left) and the validation region (right). In the left plot, events with ${S_{\mathrm {T}}^{\gamma } }$ beyond the shown range are included in the last bin. The bin contents are divided by the shown bin widths. |
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Figure 5-a:
Data to simulation comparisons in the control region. Events with ${S_{\mathrm {T}}^{\gamma } }$ beyond the shown range are included in the last bin. The bin contents are divided by the shown bin widths. |
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Figure 5-b:
Data to simulation comparisons in the validation region. The bin contents are divided by the shown bin widths. |
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Figure 6:
Comparison of measurement and prediction in the signal region in four exclusive bins of ${S_{\mathrm {T}}^{\gamma } } $. For guidance, two SUSY benchmark signal points are stacked on the SM background prediction, where the TChiWG SUSY signal point corresponds to a NLSP mass of 700 GeV and the T5Wg signal point corresponds to a gluino mass of 1750 GeV and a NLSP mass of 1700 GeV. Events with values of ${S_{\mathrm {T}}^{\gamma } }$ beyond the shown range are included in the last bin. |
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Figure 7:
Observed and expected upper cross section limits as a function of the NLSP mass for the TChiWg model together with the corresponding theoretical cross section. |
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Figure 8:
The 95% CL limits for the T5gg and T5Wg SMS models in the gluino-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 8-a:
The 95% CL limits for the T5gg SMS model in the gluino-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 8-b:
The 95% CL limits for the T5Wg SMS model in the gluino-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 9:
The 95% CL limits for the T6gg and T6Wg SMS model in the squark-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 9-a:
The 95% CL limits for the T6gg SMS model in the squark-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 9-b:
The 95% CL limits for the T6Wg SMS model in the squark-neutralino/chargino mass plane. The color scale encodes the observed upper cross section limit for each point. The lines represent the observed (black) and expected (red) exclusion contours and their uncertainties. |
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Figure 10:
Covariance and correlation matrices for the background prediction of the four signal region bins in ${S_{\mathrm {T}}^{\gamma } } $. |
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Figure 10-a:
Covariance matrix for the background prediction of the four signal region bins in ${S_{\mathrm {T}}^{\gamma } } $. |
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Figure 10-b:
Correlation matrix for the background prediction of the four signal region bins in ${S_{\mathrm {T}}^{\gamma } } $. |
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Figure 11:
Significance plots for the electroweak production models TChiWg. |
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Figure 12:
Significance plots for the strong production models T5gg (top left), T5Wg (top right), T6gg (bottom left) and T6Wg (bottom right). |
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Figure 12-a:
Significance plots for the strong production model T5gg. |
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Figure 12-b:
Significance plots for the strong production model T5Wg. |
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Figure 12-c:
Significance plots for the strong production model T6gg. |
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Figure 12-d:
Significance plots for the strong production model T6Wg. |
| Tables | |
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Table 1:
Systematic uncertainties of the individual backgrounds. |
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Table 2:
Systematic uncertainties of the electroweak and strong production SUSY signal scenarios. |
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Table 3:
Background and data yields for the separate signal region bins. The statistical uncertainty of the ${\text {e}\rightarrow \gamma } {} $ background is due to the limited size of the collected data sample. All other statistical uncertainties are due to the limited number of simulated events. The systematic uncertainties of the individual background components are added in quadrature. |
| Summary |
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We have searched for electroweak and strong production of gauginos in the framework of gauge mediated supersymmetry breaking in final states with photons and $p_{\mathrm{T}}^{\text{miss}}$. A dataset recorded at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, was analyzed. The data are found to agree with the SM expectation, without any indication of new physics. The analysis is sensitive to electroweak production and to strong production especially with compressed mass spectra, that are characterized by photons, $p_{\mathrm{T}}^{\text{miss}}$ and moderate hadronic activity in the final state. Two electroweak simplified models are used for the interpretation. The analysis excludes NLSP masses below 750 GeV at the 95% CL in the TChiWg scenario. Additionally, limits are set for four strong production simplified models based on gluino (T5gg, T5Wg) and squark (T6gg, T6Wg) pair-production. This result complements searches in the photon+jets, diphoton, and photon+leptons final states and sets the most stringent limits in the electroweak model and the compressed mass phase space in the strong production models. |
| Additional Figures | |
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Additional Figure 1:
Sketch of the control region and signal region definition. The blue area indicates the phase space of the validation region. |
| Additional Tables | |
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Additional Table 1:
Cutflow of the TChiWg benchmark signal point with a NLSP mass of 700 GeV. The preselection cut comprises the requirement of at least one loosely isolated photon with ${p_{\mathrm {T}}} > $ 180 GeV and a seed crystal energy fraction of at least 30% wrt. the full corrected photon ${p_{\mathrm {T}}} $, which was accepted by the trigger and was measured in the ECAL barrel. Furthermore, for the photon a minimal distance in $\Delta R$ of 0.5 is required wrt. to the nearest jet. Also $ \Delta \phi ( p_{\mathrm{T}}^{\text{miss}} , \text{jet} ) > $ 0.3 is required for all jets with ${p_{\mathrm {T}}} > $ 100 GeV. The FastSim strange jet veto is also included in the preselection cut. |
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Additional Table 2:
Cutflow of the T5Wg benchmark signal point with a gluino mass of 1750 GeV and a gaugino mass of 1700 GeV. The preselection cut comprises the requirement of at least one loosely isolated photon with ${p_{\mathrm {T}}} > $ 180 GeV and a seed crystal energy fraction of at least 30% wrt. the full corrected photon ${p_{\mathrm {T}}} $, which was accepted by the trigger and was measured in the ECAL barrel. Furthermore, for the photon a minimal distance in $\Delta R$ of 0.5 is required wrt. to the nearest jet. Also $ \Delta \phi ( p_{\mathrm{T}}^{\text{miss}} , \text{jet} ) > $ 0.3 is required for all jets with ${p_{\mathrm {T}}} > $ 100 GeV. The FastSim strange jet veto is also included in the preselection cut. |
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