Search for stealth supersymmetry in events with jets, either photons or leptons, and low missing momentum in pp collisions at 8 CMS.TeV (SUS-14-009)

Abstract

The results of a search for new physics in final states with jets, either photons or leptons, and no requirement on missing transverse momentum are reported. The study is based on a sample of proton-proton collisions collected at center-of-mass energy $\sqrt{s} = 8$ CMS.TeV with the CMS detector in 2012. The integrated luminosity of the sample is 19.7 fb-1. Many models of new physics predict the production of events with jets, electroweak gauge bosons, and little or no missing transverse momentum. Examples include stealth models of supersymmetry (SUSY), which predict a hidden sector at the electroweak energy scale in which SUSY is approximately conserved. The data are used to search for stealth SUSY signatures in final states with either two photons or an oppositely charged electron and muon. No excess is observed with respect to the standard model expectation and the results are used to set limits on squark pair production in the stealth SUSY framework.

Approved tables and plots

Model description

Figure Caption
feynmanSquarkDecay.png Figure 1: Decay of a squark to a quark and gaugino in stealth SUSY. Subsequent decay of the gaugino to a singlino produces a vector boson, and the singlino decay yields two gluons and a soft gravitino. The $\tilde{S}$-S mass-splitting is taken to be 10 CMS.GeV, and we assume a $\tilde{S}$ mass of 100 CMS.GeV. In the $\ell^\pm$ analysis, a range of squark masses are considered from 300 to 1000 CMS.GeV, and the chargino is fixed to be half of the squark mass rounded up to the nearest 100 CMS.GeV. In the $\gamma$ analysis, the squark mass ranges from 200 - 1400 CMS.GeV, and the neutralino mass varies from 150 to 1350 CMS.GeV with the requirement that the neutralino mass is always less than the squark mass.

Photons

Figure Caption
st_gg4J_doublePhoton_2Photon.jpg Figure 2 (left): $S_{T}$ distributions in the $\gamma$ analysis as a function of $N_{\mathrm{jets}}$ for simulated diphoton events passing selection A. The distributions are normalized to unit area. The lower plots show ratios with respect to the $N_{\mathrm{jets}} = 3$ distribution.
st_jetHt_1Photon.jpg Figure 2 (right): $S_{T}$ distributions in the $\gamma$ analysis as a function of $N_{\mathrm{jets}}$ for data events passing selection B with one photon. The distributions are normalized to unit area. The lower plots show ratios with respect to the $N_{\mathrm{jets}} = 3$ distribution.
result_doublePhoton_2Photon_4Jet.jpg Figure 4 (left): Measured $S_{T}$ distribution in comparison with the background prediction in the signal region of the $\gamma$ analysis for $N_{\mathrm{jets}} = 4$. The systematic uncertainty of the background prediction and the expected distribution of signal events for $M_{\tilde{q}} = 900$ CMS.GeV and either $M_{\tilde{\chi}_{1}^{0}} = 450$ or 850 CMS.GeV are also shown.
result_doublePhoton_2Photon_5Jet.jpg Figure 4 (right): Measured $S_{T}$ distribution in comparison with the background prediction in the signal region of the $\gamma$ analysis for $N_{\mathrm{jets}} \geq 5$. The systematic uncertainty of the background prediction and the expected distribution of signal events for $M_{\tilde{q}} = 900$ CMS.GeV and either $M_{\tilde{\chi}_{1}^{0}} = 450$ or 850 CMS.GeV are also shown.
totalLimit.jpg Figure 6: Upper limits on squark and neutralino masses from the $\gamma$ analysis. The $z$-axis indicates the observed 95% CL upper limit on the signal model cross section. The solid lines represent the observed and median expected exclusion contours at a 95% CL with the corresponding band indicating the change in exclusion from variation of the theoretical and experimental uncertainties by one standard deviation.

Leptons

Figure Caption
EventCategories_1Mu_1El_2btag_SF_stack_canvas.jpg Figure 3: Distribution of $N_{\mathrm{jets}}$ for data and simulation in the $\ell^\pm$ analysis for the top-shape control region. The uncertainty on the MC event counts is determined by varying the renormalization/factorization scale by a factor of 2(1/2).
EventCategories_1Mu_1El_0btag_SF_expectedbkg_stack_canvas.jpg Figure 5: Measured $N_{\mathrm{jets}}$ distribution in comparison with the background prediction in the signal regions of the $\ell^{\pm}$ analysis. The lower plots show the ratio of the data to the background prediction, with the systematic uncertainty in the background prediction indicated.
Limit_Plot.jpg Figure 7: Observed and median expected cross section upper limits as a function of squark mass from the $\ell^\pm$ analysis. The band about the expected limit indicates the one standard deviation experimental uncertainty. The NLO+NLL cross section with its one standard deviation uncertainty is also shown.

Additional information

The production model for the signal is a simplified model of left handed $\tilde{u}$,$\tilde{d}$, $\tilde{s}$, $\tilde{c}$ squarks.

Files Description

root file containing TH2 of signal efficiency

pdf

Stealth SUSY signal efficiency for diphoton selection, with $S_{T}$ > 1200 CMS.GeV, as a function of squark mass and neutralino mass. The signal efficiency is given separately for 4 and $\geq$ 5 jets.
result_2Photons_4Jets ROOT file containing data, signal MC, expected background, and background estimation uncertainties corresponding to Figure 4 (left). The histogram h_data represents the number of observed events in bins of 100 CMS.GeV, h_mc is the expected signal MC for a squark/neutralino mass of 900/450 CMS.GeV, and h_mc2 is the expected signal MC for a squark/neutralino mass of 900/850 CMS.GeV. The histograms bkg, bkg_bkgTotUp, and bkg_bkgTotDown contain the expected background contribution in 10 CMS.GeV bins, with the total up/down uncertainty from all sources.
result_2Photons_5Jets ROOT file containing data, signal MC, expected background, and background estimation uncertainties corresponding to Figure 4 (right). The histogram h_data represents the number of observed events in bins of 100 CMS.GeV,h_mc is the expected signal MC for a squark/neutralino mass of 900/450 CMS.GeV, and h_mc2 is the expected signal MC for a squark/neutralino mass of 900/850 CMS.GeV. The histograms bkg, bkg_bkgTotUp, and bkg_bkgTotDown contain the expected background contribution in 10 CMS.GeV bins, with the total up/down uncertainty from all sources.
photonLimits ROOT file containing the observed and expected cross section limits corresponding to Figure 6. The histogram obsXSecLimit gives the observed cross section limit for the photon analysis as a function of squark and neutralino masses. The histogram expXSecLimit gives the corresponding expected cross section limit, and the histograms expXSecLimitUp and expXSecLimitDown give the expected limits when the experimental uncertainty is varied up and down by 1 sigma.
pdf

Table 1: Event counts for lepton analysis with 0 b-tags, binnded exclusive bins of jet multiplicity, and three inclusive $S_{T}$ bins. We apply thresholds of $S_{T}$ = 300 CMS.GeV for $M_{\tilde{q}}$ = 300 CMS.GeV, $S_{T}$ = 700 CMS.GeV for $M_{\tilde{q}}$ values of 400 and 500 CMS.GeV, and $S_{T}$ =1200 CMS.GeV for $M_{\tilde{q}}$ $\geq$ 600 CMS.GeV.

Table 2: Event counts for lepton analysis in $\geq$ 2 b-tag control sample, binned in exclusive jet multiplicity, and three inclusive $S_{T}$ bins. The uncertainty on the MC event counts is determined by varying the renormalization/factorization scale by a factor of 2(1/2).

cutFlowTables Cut flows for the photon (Table 1) and lepton (Table 2) analyses with efficiencies for benchmark signal points. The full selection efficiencies for the signal points in the search region are also shown for the photon (bottom of Table 1) and lepton (Table 3) analyses.
Topic attachments
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JPEGjpg EventCategories_1Mu_1El_2btag_SF_stack_canvas.jpg r8 r7 r6 r5 r4 manage 75.8 K 2014-11-13 - 18:40 MarcWeinberg  
PDFpdf EventCategories_1Mu_1El_2btag_SF_stack_canvas.pdf r6 r5 r4 r3 r2 manage 32.8 K 2014-11-13 - 17:32 BenCarlson  
JPEGjpg Limit_Plot.jpg r8 r7 r6 r5 r4 manage 60.9 K 2014-11-14 - 10:06 MarcWeinberg  
PDFpdf Limit_Plot.pdf r8 r7 r6 r5 r4 manage 13.6 K 2014-11-14 - 10:08 MarcWeinberg  
PDFpdf SignalCutFlowTable.pdf r1 manage 11.7 K 2014-09-02 - 23:18 BenCarlson  
PDFpdf SummaryEventCounts.pdf r2 r1 manage 50.9 K 2014-12-02 - 18:29 BenCarlson  
PDFpdf SummaryEventCounts_.pdf r3 r2 r1 manage 50.5 K 2014-09-08 - 20:01 BenCarlson  
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PDFpdf cutFlowTables.pdf r3 r2 r1 manage 32.1 K 2014-09-08 - 23:48 MarcWeinberg  
JPEGjpg feynmanSquarkDecay.jpg r1 manage 7.8 K 2014-11-07 - 20:37 MarcWeinberg  
PDFpdf feynmanSquarkDecay.pdf r2 r1 manage 10.2 K 2014-11-07 - 20:37 MarcWeinberg  
PNGpng feynmanSquarkDecay.png r4 r3 r2 r1 manage 39.8 K 2014-11-10 - 15:02 MarcWeinberg  
Unknown file formatroot result_2Photons_4Jets.root r4 r3 r2 r1 manage 7.5 K 2014-09-02 - 22:23 MarcWeinberg  
Unknown file formatroot result_2Photons_5Jets.root r4 r3 r2 r1 manage 7.5 K 2014-09-02 - 22:23 MarcWeinberg  
JPEGjpg result_doublePhoton_2Photon_4Jet.jpg r7 r6 r5 r4 r3 manage 61.3 K 2014-11-19 - 05:12 MarcWeinberg  
PDFpdf result_doublePhoton_2Photon_4Jet.pdf r7 r6 r5 r4 r3 manage 17.9 K 2014-11-19 - 05:16 MarcWeinberg  
JPEGjpg result_doublePhoton_2Photon_5Jet.jpg r7 r6 r5 r4 r3 manage 61.8 K 2014-11-19 - 05:17 MarcWeinberg  
PDFpdf result_doublePhoton_2Photon_5Jet.pdf r7 r6 r5 r4 r3 manage 18.4 K 2014-11-19 - 05:19 MarcWeinberg  
JPEGjpg st_gg4J_doublePhoton_2Photon.jpg r8 r7 r6 r5 r4 manage 54.1 K 2014-11-13 - 07:05 MarcWeinberg  
PDFpdf st_gg4J_doublePhoton_2Photon.pdf r8 r7 r6 r5 r4 manage 16.6 K 2014-11-13 - 07:04 MarcWeinberg  
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PDFpdf stealth_susy_signal_efficiency_diphoton.pdf r1 manage 57.5 K 2014-08-29 - 20:32 AlexeyFerapontov  
Unknown file formatroot stealth_susy_signal_efficiency_diphoton.root r1 manage 6.8 K 2014-08-29 - 20:32 AlexeyFerapontov  
JPEGjpg totalLimit.jpg r7 r6 r5 r4 r3 manage 75.7 K 2014-11-18 - 16:49 MarcWeinberg  
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Topic revision: r44 - 2014-12-03 - KeithUlmer
 
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