Search for new physics with same-sign isolated di-lepton events with jets and missing transverse energy at the LHC

Abstract

The results of searches for new physics in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state are presented. The searches use an integrated luminosity of 35 pb−1 of pp collision data at a centre-of- mass energy of 7 TeV collected by the CMS experiment at the LHC. The observed numbers of events agree with the standard model predictions, and no evidence for new physics is found. To facilitate the interpretation of our data in a broader range of new physics scenarios, information on our event selection, detector response, and efficiencies is provided.

Companion analysis: SUSY with sneutrino as the LSP

Approved Plots from SUS-10-004 ( click on plot to get .pdf )

Table Abbreviated Caption
table1.png Table 1: Validation of the TL method. The number of observed events is compared to the number of predicted events in simulation (first two columns) and in a background-dominated control region with relaxed selection criteria (last two columns). The simulation is normalized to 35 pb−1 . The first and second uncertainties in the number of predicted events in data are statistical and systematic, respectively
table2.png Table 2: Observed and estimated background yields for all analyses. The rows labeled “pre-dicted BG” refer to the sum of the data-driven estimates of the fake lepton contributions, and the residual contributions predicted by the simulation. The rows labeled “MC” refer to the background as predicted from the simulation alone. Rows labeled “observed” show the actual number of events seen in data. The last column (95% CL UL Yield) represents observed upper limits on event yields from new physics.

Figure Abbreviated Caption
Figure1.png Figure 1 : An example of a process involving the production and decays of SUSY particles, which gives rise to two same-sign prompt leptons, jets, and missing transverse energy.
Figure2a.png Figure 2a : HT versus ET scatter plots for baseline region. Overlay of the three observed events with the expected signal distribution for LM0. The three observed events all scatter in the lower left corner of the plot.
Figure2b.png Figure 2b : HT versus ET scatter plots for baseline region. Scatter plot of the background in data when only one of the two leptons is required to be isolated.
Figure3.png Figure 3 : HT Trigger efficiency as a function of the reconstructed HT for three data-collecting periods: 7 pb−1 with HT 1, 10 pb−1 with HT 2, and 18 pb−1 with HT 3.
Figure4a.png Figure 4a : Electron (left) and muon (right) TL probability TL computed from QCD multijet events with different requirements on the minimum p T of the away-jet. The probabilities shown are projections of the two-dimensional function TL (η, p T ) onto the p T axis.
Figure4a.png Figure 4b : Electron (left) and muon (right) TL probability TL computed from QCD multijet events with different requirements on the minimum p T of the away-jet. The probabilities shown are projections of the two-dimensional function TL (η, p T ) onto the p T axis.
Figure5a.png Figure 5a : The lepton isolation efficiency for one (solid squares) and two (open squares) leptons as a function of the relative isolation parameter cut. Also shown is the predicted double-lepton efficiency if the two lepton efficiencies are assumed to be independent of each other. Only the dimuon sample is shown here
Figure5b.png Figure 5b : The lepton isolation efficiency as a function of the ET cut for electrons and muons with different requirements on the lepton impact parameter.
Figure6a.png Figure 6a : Isolation variable distributions obtained with the BTag-and-probe method for muons (left) and electrons (right). Efficiencies for the Rel Iso < 0.15 (first bin in the distributions shown) are explicitly quoted
Figure6b.png Figure 6b : Isolation variable distributions obtained with the BTag-and-probe method for muons (left) and electrons (right). Efficiencies for the Rel Iso < 0.15 (first bin in the distributions shown) are explicitly quoted
Figure7.png Figure 7 : (Left) The probability to mismeasure the electron charge as a function of η in the p T range 10−100 GeV, as obtained from simulation. (Right) Same-sign ee invariant mass distribution in data compared with the Z → ee expectation from simulation
Figure8.png Figure 8 : A visual summary of the observed number of data events, the expected number of background events, and the composition of the background for the four search regions
Figure9a.png Figure 9a : Electron, muon (left) and τh (right) selection efficiencies as a function of p T . The results of the fits described in the text are shown by the dotted lines.
Figure9b.png Figure 9b : Electron, muon (left) and τh (right) selection efficiencies as a function of p T . The results of the fits described in the text are shown by the dotted lines.
Figure10.png Figure 10 : Exclusion contour in the m0 —m1/2 plane for CMSSM as described in the text. Comparing the width of the red shaded band (theoretical uncertainty) around the blue curve with the difference between the solid blue and dashed black curves shows that the imperfections in the simple efficiency model described in the text are small compared to the theoretical uncertainties.

Link to the Paper in arXiv:1104.3168

-- SanjayPadhi - 25-Feb-2011

Topic attachments
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PDFpdf Figure1.pdf r1 manage 32.3 K 2011-04-29 - 00:55 SanjayPadhi  
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