CMS-PAS-SUS-16-023 | ||
Search for supersymmetry in final states with at least one photon and $E_{\mathrm{T}}^{\text{miss}}$ in pp collisions at $\sqrt{s}=$ 13 TeV | ||
CMS Collaboration | ||
August 2016 | ||
Abstract: A search for electroweak production of gauginos is presented using the first LHC Run II data at a center-of-mass energy of 13 TeV. The used data set has been recorded with the CMS detector and corresponds to an integrated luminosity of 2.3 fb$^{-1}$. In gauge-mediated supersymmetry breaking (GMSB) models the gauginos can decay to photons, or other standard model bosons, and gravitinos. The final state considered in this search is characterized by photons and missing transverse energy. Since in electroweak production scenarios the expected hadronic activity is low compared to strong production, no jet requirements are used. Additionally, gluino pair production models are considered, where the analysis does not lose sensitivity in scenarios with compressed mass spectra. The observed data are in agreement with the standard model prediction and limits are set on different models of GMSB. | ||
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Feynman diagram of the dominant ${\tilde{\chi}^\pm _{1}} - {\tilde{\chi}^{0}_{2}}$ production mechanism and a typical decay chain in scenarios with a bino-like ${\tilde{\chi}^{0}_{1}}$ and wino-like ${\tilde{\chi}^{0}_{2}}$ and ${\tilde{\chi}^\pm _{1}} $. |
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Figure 2:
Feynman diagram corresponding to the TChiWg simplified model. |
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Figure 3-a:
Feynman diagrams of the T5gg (a) and T5Wg (b) simplified models. |
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Figure 3-b:
Feynman diagrams of the T5gg (a) and T5Wg (b) simplified models. |
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Figure 4:
Sketch of the control (CR) and signal region (SR) definitions. The validation region (VR) is not defined in the ${\mathcal {S}}- {M_\mathrm {T}}$ plane, but embedded in the SR with the additional condition $ { S_\mathrm {T}^{ {\gamma }}}<$ 600 GeV. This corresponds approximately to the bottom-left corner of the SR, which is therefore illustrated as a blurred region. |
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Figure 5-a:
The ${\mathcal {S}}$ and ${M_\mathrm {T}}$ distributions after the preselection. The overflow is contained in the last bin shown and the bin contents are divided by the bin widths. |
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Figure 5-b:
The ${\mathcal {S}}$ and ${M_\mathrm {T}}$ distributions after the preselection. The overflow is contained in the last bin shown and the bin contents are divided by the bin widths. |
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Figure 6:
Template fit result: The post-fit distributions for ($\gamma +$)jets and V($+\gamma $) together with the total fit distribution stacked onto the fixed backgrounds. Events containing zero jets are counted in the last shown bin. The values in the legend are the resulting scale factors. |
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Figure 7-a:
Comparison of the total background prediction to data in the control region without a b-jet veto. a,b: ${E_{\mathrm {T}}^{\text {miss}}} $ significance (a) and transverse mass (b). c,d: ${ S_\mathrm {T}^{ {\gamma }}}$ (c) and leading photon ${p_{\mathrm {T}}} $ (d). The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 7-b:
Comparison of the total background prediction to data in the control region without a b-jet veto. a,b: ${E_{\mathrm {T}}^{\text {miss}}} $ significance (a) and transverse mass (b). c,d: ${ S_\mathrm {T}^{ {\gamma }}}$ (c) and leading photon ${p_{\mathrm {T}}} $ (d). The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 7-c:
Comparison of the total background prediction to data in the control region without a b-jet veto. a,b: ${E_{\mathrm {T}}^{\text {miss}}} $ significance (a) and transverse mass (b). c,d: ${ S_\mathrm {T}^{ {\gamma }}}$ (c) and leading photon ${p_{\mathrm {T}}} $ (d). The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 7-d:
Comparison of the total background prediction to data in the control region without a b-jet veto. a,b: ${E_{\mathrm {T}}^{\text {miss}}} $ significance (a) and transverse mass (b). c,d: ${ S_\mathrm {T}^{ {\gamma }}}$ (c) and leading photon ${p_{\mathrm {T}}} $ (d). The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 8-a:
Comparison of the total background prediction to data in the control region with the additional requirement of exactly one lepton. a: missing transverse energy. b: ${E_{\mathrm {T}}^{\text {miss}}}$ significance. The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 8-b:
Comparison of the total background prediction to data in the control region with the additional requirement of exactly one lepton. a: missing transverse energy. b: ${E_{\mathrm {T}}^{\text {miss}}}$ significance. The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 9-a:
Comparison of the total background prediction to data in the validation region. a: leading photon ${p_{\mathrm {T}}} $. b: ${ S_\mathrm {T}^{ {\gamma }}}$. The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 9-b:
Comparison of the total background prediction to data in the validation region. a: leading photon ${p_{\mathrm {T}}} $. b: ${ S_\mathrm {T}^{ {\gamma }}}$. The overflow is contained in the last bin. The bin contents are divided by the bin widths. |
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Figure 10:
Background and data distributions in the signal region using the final binning in ${ S_\mathrm {T}^{ {\gamma }}}$. The last bin contains the overflow. The background and signal histograms are stacked. |
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Figure 11:
The 95% CL limits for the GGM model in the bino-wino 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 12:
Observed and expected upper cross section limits as a function of the NLSP mass for the TChiWg model together with the theoretical cross section. |
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Figure 13:
The 95% CL limits for the T5gg model in the gluino-neutralino 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 14:
The 95% CL limits for the T5Wg model in the gluino-neutralino 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. |
Tables | |
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Table 1:
Systematic uncertainties of the separate backgrounds. The uncertainties are relative to the respective backgrounds. |
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Table 2:
Yields for the individual SR bins. For the total systematic uncertainties the correlation term for the systematic uncertainties of ${\mathrm {V}(+ {\gamma })}$ and ${( {\gamma }+)\text {jets}}$ has been considered. |
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Table 3:
Individual background yields for the separate signal region bins. The statistical uncertainty of the ${ {\mathrm {e}}\to {\gamma }}$ 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. |
Summary |
A search for the production of supersymmetric particles decaying to photons is presented. The data sample used corresponds to 2.3 fb$^{-1}$ of pp collisions recorded with the CMS detector in 2015 at $ \sqrt{s} = $ 13 TeV. A cut-and-count experiment is performed in three exclusive search bins. The observed event counts are in agreement with the SM prediction. Exclusion limits at the 95% CL are set for a general gauge mediation model of electroweak production and the simplified model TChiWg. The limits for the electroweak production models cannot be improved with respect to the 8 TeV search. A much larger sensitivity is expected with more integrated luminosity collected at $ \sqrt{s} = $ 13 TeV. Additionally, limits are set for two simplified models (T5gg, T5Wg) assuming gluino pair production. The currently best CMS limits are improved in regions with large NLSP masses. |
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Compact Muon Solenoid LHC, CERN |