Search for physics beyond the standard model in events with two leptons, jets, and missing transverse energy in pp collisions at sqrt(s)=8 TeV
Physics Analysis Summary
Link to
PAS-SUS-12-019
.
Abstract
This note presents a search for physics beyond the standard model in final states with two opposite-sign same-flavor leptons, jets, and missing transverse energy, in a sample of 8 TeV pp collisions collected with the CMS detector at the CERN LHC. The experimental analysis focuses on searches for a kinematic edge in the invariant mass distribution of the opposite-sign same-flavor lepton pair. The size of the data sample corresponds to an integrated luminosity of 19.4 fb-1.
We do not observe evidence for a statistically significant signal.
Acronyms
- SF = same-flavor, used to abbreviate the sample of two opposite-sign leptons of same flavor, i.e, ee + μμ
- OF = opposite-flavor, used to abbreviate the sample of two opposite-sign leptons that are of opposite (different) flavor, i.e., eμ
- FS = flavor-symmetric, used to denote any process that produces the same rate of SF and OF lepton pairs, e.g., top pair production, W+W-
- DY = Drell-Yan
Preselection
- Nlep ≥ 2 with pT > 20 GeV and |η| < 2.4
- Njets ≥ 2 with pT > 40 GeV and |η| < 3.0
Signal regions
- (Njets ≥ 2 .AND. MET > 150 GeV ) .OR. (Njets ≥ 3 .AND. MET > 100 GeV)
- central region (both leptons within |η| < 1.4)
- kinematic fit in 20 < m(ll) < 300 GeV
- counting experiment in 20 < m(ll) < 70 GeV
- forward region (at least one lepton with |η| > 1.4)
- kinematic fit in 20 < m(ll) < 300 GeV
- counting experiment in 20 < m(ll) < 70 GeV
Plots (click on plot to get PDF version)
Figure |
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Figure 1a : MET distributions for SF sample for m(ll) > 20 GeV and Njets ≥ 2. The error bars show the statistical uncertainties of data and MC samples, while the shaded band depicts the MC statistical and systematic uncertainty added in quadrature |
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Figure 1b : MET distributions for OF sample for m(ll) > 20 GeV and Njets ≥ 2. The error bars show the statistical uncertainties of data and MC samples, while the shaded band depicts the MC statistical and systematic uncertainty added in quadrature |
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Figure 2a : Fit results for the signal-plus-background hypothesis in comparison to the measured dilepton mass distributions, in the central region, projected on the SF event sample. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. The flavor-symmetric background is denoted as FS and is displayed with a black dashed line. The Drell–Yan contribution is denoted as DY and is displayed with a red dashed line. The extracted signal component is denoted as Signal and is displayed with a green dashed line. |
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Figure 2b : Fit results for the signal-plus-background hypothesis in comparison to the measured dilepton mass distributions, in the central region, projected on the OF event sample. The combined fit shape is shown as a blue, solid line. |
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Figure 2c : Fit results for the signal-plus-background hypothesis in comparison to the measured dilepton mass distributions, in the forward region, projected on the SF event sample. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. The flavor-symmetric background is denoted as FS and is displayed with a black dashed line. The Drell–Yan contribution is denoted as DY and is displayed with a red dashed line. The extracted signal component is denoted as Signal and is displayed with a green dashed line. |
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Figure 2d : Fit results for the signal-plus-background hypothesis in comparison to the measured dilepton mass distributions, in the forward region, projected on the OF event sample. The combined fit shape is shown as a blue, solid line. |
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Figure 3a : Comparison between the observed and estimated SM background dilepton mass distributions in the central region, where the SM backgrounds are evaluated from control samples (see CMS-PAS-SUS-12-019 for details) rather than from the fit. |
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Figure 3b : Comparison between the observed and estimated SM background dilepton mass distributions in the forward region, where the SM backgrounds are evaluated from control samples (see CMS-PAS-SUS-12-019 for details) rather than from the fit. |
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Figure 4a : Data compared with SM simulation for the SF event sample in the central rapidity region. Example signal scenarios based on the pair production of bottom-squarks is shown (see CMS-PAS-SUS-12-019 for details). |
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Figure 4b : Data compared with SM simulation for the OF event sample in the central rapidity region. Example signal scenarios based on the pair production of bottom-squarks is shown (see CMS-PAS-SUS-12-019 for details). |
Tables
Table |
Caption |
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Table 1: Results for RSF/OF in the signal regions. The values of rμe and RT listed for the control region method are not used directly in the analysis and are listed for purposes of comparison only. |
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Table 2: Result of the unbinned maximum likelihood fit. Event yields measured and estimated in the signal regions. Statistical and systematic uncertainties are added in quadrature. |
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Table 3: Results of the counting experiment. Event yields measured and estimated in the signal regions. Statistical and systematic uncertainties are added in quadrature. |
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Table 4: Event yields for the mbottom-squark = 225 GeV, mneutralino-two = 150 GeV signal model for different selection requirements. The signal is normalized to the integrated luminosity of 19.4 fb-1 using a cross section of 9.9 pb. The uncertainties are statistical. |
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Table 5: Event yields for the mbottom-squark = 350 GeV, mneutralino-two = 275 GeV signal model for different selection requirements. The signal is normalized to the integrated luminosity of 19.4 fb-1 using a cross section of 807 fb. The uncertainties are statistical. |
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Table 6: Event yields for the mbottom-squark = 400 GeV, mneutralino-two = 150 GeV signal model for different selection requirements. The signal is normalized to the integrated luminosity of 19.4 fb-1 using a cross section of 357 fb. The uncertainties are statistical. |
Auxiliary material
Figure |
Caption |
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Background hypothesis fit to the dilepton mass distributions, in the central rapidity region projected on the SF event sample. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. |
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Background hypothesis fit to the dilepton mass distributions, in the central rapidity region projected on the OF event sample. The combined fit shape is shown as a blue, solid line. |
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Background hypothesis fit to the dilepton mass distributions, in the forward rapidity region projected on the SF event sample. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. |
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Background hypothesis fit to the dilepton mass distributions, in the forward rapidity region projected on the OF event sample. The combined fit shape is shown as a blue, solid line. |
Figure |
Caption |
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Signal plus background hypothesis fit to the same-flavor (SF) dilepton mass distributions, in simulation with signal injection. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. |
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Signal plus background hypothesis fit to the opposite-flavor (OF) dilepton mass distributions, in MC simulation with signal injection. The combined fit shape is shown as a blue, solid line. |
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Background hypothesis fit to the same-flavor (SF) dilepton mass distributions, in simulation with signal injection. The combined fit shape is shown as a blue, solid line. The individual fit components are indicated by dashed lines. |
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Background hypothesis fit to the same-flavor (OF) dilepton mass distributions, in simulation with signal injection. The combined fit shape is shown as a blue, solid line. |
SLHA files for models containing an edge
The SLHA files for the scan producing an edge at 70
GeV can be found here:
link to SLHA files
The SLHA files for the scan including sleptons and producing an edge in different positions depending on the mass hierarchy can be found here:
link to SLHA files
Further information
This analysis is documented in
CMS-PAS-SUS-12-019.
The Table and Figure numbers in this twiki correspond to the table and figure numbers in the document.
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KostasTheofilatos - 21 Jul 2014