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

CMS Collaboration

TL;DR

This CMS study searches for new physics in events with two same-sign isolated leptons, jets, and missing transverse energy using 35 pb$^{-1}$ of 7 TeV pp data. By employing two trigger strategies (lepton-based and $H_T$-based) and a suite of data-driven background-estimation techniques (tight-loose methods, factorized efficiencies, and BTag-and-probe), the analysis achieves robust background predictions across multiple final states, including electrons, muons, and hadronic $\tau$ decays. No excess over the Standard Model is observed, and 95% CL upper limits are set on potential new-physics yields in four signal regions; the results are interpreted with a generator-level framework to constrain a broad class of models, including CMSSM scenarios. The study provides detailed acceptance and efficiency information to facilitate reinterpretation in future theoretical and experimental analyses, thereby extending constraints beyond prior LEP/Tevatron limits and informing search strategies at the LHC for similar signatures.

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 inverse picobarns 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.

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

TL;DR

This CMS study searches for new physics in events with two same-sign isolated leptons, jets, and missing transverse energy using 35 pb of 7 TeV pp data. By employing two trigger strategies (lepton-based and -based) and a suite of data-driven background-estimation techniques (tight-loose methods, factorized efficiencies, and BTag-and-probe), the analysis achieves robust background predictions across multiple final states, including electrons, muons, and hadronic decays. No excess over the Standard Model is observed, and 95% CL upper limits are set on potential new-physics yields in four signal regions; the results are interpreted with a generator-level framework to constrain a broad class of models, including CMSSM scenarios. The study provides detailed acceptance and efficiency information to facilitate reinterpretation in future theoretical and experimental analyses, thereby extending constraints beyond prior LEP/Tevatron limits and informing search strategies at the LHC for similar signatures.

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 inverse picobarns 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.

Paper Structure

This paper contains 18 sections, 10 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The CMS Detector
  3. Reconstruction of Leptons, Missing Energy, and Jets
  4. Search Regions
  5. Searches using Lepton Triggers
  6. Searches using Hadronic Triggers
  7. Background Estimation
  8. Searches using Lepton Triggers
  9. Search using Hadronic Triggers, Electrons, and Muons
  10. Search using Hadronic Triggers and $\tau_h$
  11. Comparison of Leptonic and $H_T$-Triggered Analyses with Electrons and Muons in the Final State
  12. Electron Charge Mismeasurement
  13. Signal Acceptance and Efficiency Systematic Uncertainties
  14. Summary of Results
  15. Interpretation of Results
  16. ...and 3 more sections

Figures (10)

  • 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.
  • Figure 2: $H_T$ versus $E_{T}^{\rm miss}$ scatter plots for baseline region. (Left) 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. (Right) Scatter plot of the background in data when only one of the two leptons is required to be isolated.
  • Figure 3: $H_T$ Trigger efficiency as a function of the reconstructed $H_T$ for three data-collecting periods: 7 pb$^{-1}$ with $H_{T}1$, 10 pb$^{-1}$ with $H_{T}2$, and 18 pb$^{-1}$ with $H_{T}3$.
  • Figure 4: Electron (left) and muon (right) TL probability $\epsilon_{TL}$ 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 $\epsilon_{TL}(\eta , p_T )$ onto the $p_T$ axis.
  • Figure 5: (Left) 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. (Right) The lepton isolation efficiency as a function of the $E_{T}^{\rm miss}$ cut for electrons and muons with different requirements on the lepton impact parameter. Details are given in the text.
  • ...and 5 more figures