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ATLAS_2012_I1112263

3 lepton plus missing transverse energy SUSY search
Experiment: ATLAS (LHC)
Inspire ID: 1112263
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • BSM signal events at 7000 GeV.

Search for SUSY using events with 3 leptons in association with missing transverse energy in proton-proton collisions at a centre-of-mass energy of 7 TeV. The data sample has a total integrated luminosity of 2.06 fb$^{-1}$. There is no reference data and in addition to the control plots from the paper the number of events in the two signal regions, correctly normalized to an integrated luminosity 2.06 fb$^{-1}$, are calculated.

Source code: ATLAS_2012_I1112263.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Tools/RivetMT2.hh"

namespace Rivet {


  /// @author Peter Richardson
  class ATLAS_2012_I1112263 : public Analysis {
  public:

    /// Constructor
    ATLAS_2012_I1112263()
      : Analysis("ATLAS_2012_I1112263")
    {    }


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {

      // projection to find the electrons
      IdentifiedFinalState elecs(Cuts::abseta < 2.47 && Cuts::pT > 10*GeV);
      elecs.acceptIdPair(PID::ELECTRON);
      declare(elecs, "elecs");

      // projection to find the muons
      IdentifiedFinalState muons(Cuts::abseta < 2.4 && Cuts::pT > 10*GeV);
      muons.acceptIdPair(PID::MUON);
      declare(muons, "muons");

      // for pTmiss
      declare(VisibleFinalState(Cuts::abseta < 4.9),"vfs");

      VetoedFinalState vfs;
      vfs.addVetoPairId(PID::MUON);

      /// Jet finder
      declare(FastJets(vfs, FastJets::ANTIKT, 0.4), "AntiKtJets04");

      // all tracks (to do deltaR with leptons)
      declare(ChargedFinalState(Cuts::abseta < 3.0),"cfs");

      // Book histograms
      _hist_leptonpT_SR1.push_back(bookHisto1D("hist_lepton_pT_1_SR1",11,0.,220.));
      _hist_leptonpT_SR1.push_back(bookHisto1D("hist_lepton_pT_2_SR1", 7,0.,140.));
      _hist_leptonpT_SR1.push_back(bookHisto1D("hist_lepton_pT_3_SR1", 8,0.,160.));
      _hist_leptonpT_SR2.push_back(bookHisto1D("hist_lepton_pT_1_SR2",11,0.,220.));
      _hist_leptonpT_SR2.push_back(bookHisto1D("hist_lepton_pT_2_SR2", 7,0.,140.));
      _hist_leptonpT_SR2.push_back(bookHisto1D("hist_lepton_pT_3_SR2", 8,0.,160.));
      _hist_etmiss_SR1_A = bookHisto1D("hist_etmiss_SR1_A",15,10.,310.);
      _hist_etmiss_SR1_B = bookHisto1D("hist_etmiss_SR1_B", 9,10.,190.);
      _hist_etmiss_SR2_A = bookHisto1D("hist_etmiss_SR2_A",15,10.,310.);
      _hist_etmiss_SR2_B = bookHisto1D("hist_etmiss_SR2_B", 9,10.,190.);
      _hist_mSFOS= bookHisto1D("hist_mSFOF",9,0.,180.);

      _count_SR1 = bookHisto1D("count_SR1", 1, 0., 1.);
      _count_SR2 = bookHisto1D("count_SR2", 1, 0., 1.);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // Get the jet candidates
      Jets cand_jets;
      foreach (const Jet& jet, apply<FastJets>(event, "AntiKtJets04").jetsByPt(20.0*GeV) ) {
        if ( fabs( jet.eta() ) < 2.8 ) {
          cand_jets.push_back(jet);
        }
      }

      // Candidate muons
      Particles cand_mu;
      Particles chg_tracks =
        apply<ChargedFinalState>(event, "cfs").particles();
      foreach ( const Particle & mu, apply<IdentifiedFinalState>(event, "muons").particlesByPt() ) {
        double pTinCone = -mu.pT();
        foreach ( const Particle & track, chg_tracks ) {
          if ( deltaR(mu.momentum(),track.momentum()) <= 0.2 )
            pTinCone += track.pT();
        }
        if ( pTinCone < 1.8*GeV )
          cand_mu.push_back(mu);
      }

      // Candidate electrons
      Particles cand_e;
      foreach ( const Particle & e, apply<IdentifiedFinalState>(event, "elecs").particlesByPt() ) {
        double eta = e.eta();
        // Remove electrons with pT<15 in old veto region
        // (NOT EXPLICIT IN THIS PAPER BUT IN SIMILAR 4 LEPTON PAPER and THIS DESCRPITION
        //  IS MUCH WORSE SO ASSUME THIS IS DONE)
        if ( fabs(eta)>1.37 && fabs(eta) < 1.52 && e.perp()< 15.*GeV)
          continue;
        double pTinCone = -e.perp();
        foreach ( const Particle & track, chg_tracks ) {
          if ( deltaR(e.momentum(),track.momentum()) <= 0.2 )
            pTinCone += track.pT();
        }
        if (pTinCone/e.perp()<0.1) {
          cand_e.push_back(e);
        }
      }

      // Resolve jet/lepton ambiguity
      // (NOT EXPLICIT IN THIS PAPER BUT IN SIMILAR 4 LEPTON PAPER and THIS DESCRPITION
      //  IS MUCH WORSE SO ASSUME THIS IS DONE)
      Jets recon_jets;
      foreach ( const Jet& jet, cand_jets ) {
        bool away_from_e = true;
        foreach ( const Particle & e, cand_e ) {
          if ( deltaR(e.momentum(),jet.momentum()) <= 0.2 ) {
            away_from_e = false;
            break;
          }
        }
        if ( away_from_e )
          recon_jets.push_back( jet );
      }

      // Only keep electrons more than R=0.4 from jets
      Particles recon_e;
      foreach ( const Particle & e, cand_e ) {
        bool away = true;
        foreach ( const Jet& jet, recon_jets ) {
          if ( deltaR(e.momentum(),jet.momentum()) < 0.4 ) {
            away = false;
            break;
          }
        }
        // ... and 0.1 from any muons
        if ( ! away ) {
          foreach ( const Particle & mu, cand_e ) {
            if ( deltaR(mu.momentum(),e.momentum()) < 0.1 ) {
              away = false;
              break;
            }
          }
        }
        if ( away )
          recon_e.push_back( e );
      }
      // Only keep muons more than R=0.4 from jets
      Particles recon_mu;
      foreach ( const Particle & mu, cand_mu ) {
        bool away = true;
        foreach ( const Jet& jet, recon_jets ) {
          if ( deltaR(mu.momentum(),jet.momentum()) < 0.4 ) {
            away = false;
            break;
          }
        }
        // ... and 0.1 from any electrona
        if ( ! away ) {
          foreach ( const Particle & e, cand_e ) {
            if ( deltaR(mu.momentum(),e.momentum()) < 0.1 ) {
              away = false;
              break;
            }
          }
        }
        if ( away )
          recon_mu.push_back( mu );
      }

      // pTmiss
      Particles vfs_particles =
        apply<VisibleFinalState>(event, "vfs").particles();
      FourMomentum pTmiss;
      foreach ( const Particle & p, vfs_particles ) {
        pTmiss -= p.momentum();
      }
      double eTmiss = pTmiss.pT();

      // Now only use recon_jets, recon_mu, recon_e

      // Reject events with wrong number of leptons
      if ( recon_mu.size() + recon_e.size() != 3 ) {
        MSG_DEBUG("To few charged leptons left after selection");
        vetoEvent;
      }

      // ATLAS calo problem
      if (rand()/static_cast<double>(RAND_MAX) <= 0.42) {
        foreach ( const Particle & e, recon_e ) {
          double eta = e.eta();
          double phi = e.azimuthalAngle(MINUSPI_PLUSPI);
          if (inRange(eta, -0.1, 1.5) && inRange(phi, -0.9, -0.5)) vetoEvent;
        }
        foreach ( const Jet & jet, recon_jets ) {
          const double eta = jet.rapidity();
          const double phi = jet.azimuthalAngle(MINUSPI_PLUSPI);
          if (jet.perp() > 40*GeV && inRange(eta, -0.1, 1.5) && inRange(phi, -0.9, -0.5)) vetoEvent;
        }
      }

      if ( !( !recon_e .empty() && recon_e[0] .perp() > 25*GeV) &&
           !( !recon_mu.empty() && recon_mu[0].perp() > 20*GeV) ) {
        MSG_DEBUG("Hardest lepton fails trigger");
        vetoEvent;
      }

      // eTmiss cut
      if (eTmiss < 50*GeV) vetoEvent;

      // Check at least 1 SFOS pair
      double mSFOS=1e30, mdiff=1e30*GeV;
      size_t nSFOS=0;
      for (size_t ix = 0; ix < recon_e.size(); ++ix) {
        for (size_t iy = ix+1; iy < recon_e.size(); ++iy) {
          if (recon_e[ix].pid()*recon_e[iy].pid() > 0) continue;
          ++nSFOS;
          double mtest = (recon_e[ix].momentum() + recon_e[iy].momentum()).mass();
          // Veto is mass<20
          if (mtest < 20*GeV) vetoEvent;
          if (fabs(mtest - 90*GeV) < mdiff) {
            mSFOS = mtest;
            mdiff = fabs(mtest - 90*GeV);
          }
        }
      }
      for (size_t ix = 0; ix < recon_mu.size(); ++ix) {
        for (size_t iy = ix+1; iy < recon_mu.size(); ++iy) {
          if (recon_mu[ix].pid()*recon_mu[iy].pid() > 0) continue;
          ++nSFOS;
          double mtest = (recon_mu[ix].momentum() + recon_mu[iy].momentum()).mass();
          // Veto is mass < 20*GeV
          if (mtest < 20*GeV) vetoEvent;
          if (fabs(mtest - 90*GeV) < mdiff) {
            mSFOS = mtest;
            mdiff = fabs(mtest - 90*GeV);
          }
        }
      }
      // Require at least 1 SFOS pair
      if (nSFOS == 0) vetoEvent;
      // b-jet veto in SR!
      if (mdiff > 10*GeV) {
        foreach (const Jet & jet, recon_jets ) {
          if (jet.bTagged() && rand()/static_cast<double>(RAND_MAX) <= 0.60) vetoEvent;
        }
      }

	  // Histogram filling
	  const double weight = event.weight();

      // Region SR1, Z depleted
      if (mdiff > 10*GeV) {
        _count_SR1->fill(0.5, weight);
        _hist_etmiss_SR1_A->fill(eTmiss, weight);
        _hist_etmiss_SR1_B->fill(eTmiss, weight);
        _hist_mSFOS->fill(mSFOS, weight);
      }
      // Region SR2, Z enriched
      else {
        _count_SR2->fill(0.5, weight);
        _hist_etmiss_SR2_A->fill(eTmiss, weight);
        _hist_etmiss_SR2_B->fill(eTmiss, weight);
      }
      // Make the control plots
      // lepton pT
      size_t ie=0, imu=0;
      for (size_t ix = 0; ix < 3; ++ix) {
        Histo1DPtr hist = (mdiff > 10*GeV) ? _hist_leptonpT_SR1[ix] :  _hist_leptonpT_SR2[ix];
        double pTe  = (ie  < recon_e .size()) ? recon_e [ie ].perp() : -1*GeV;
        double pTmu = (imu < recon_mu.size()) ? recon_mu[imu].perp() : -1*GeV;
        if (pTe > pTmu) {
          hist->fill(pTe, weight);
          ++ie;
        } else {
          hist->fill(pTmu, weight);
          ++imu;
        }
      }

    }


    void finalize() {
      const double norm = crossSection()/femtobarn*2.06/sumOfWeights();
      // These are number of events at 2.06fb^-1 per 20 GeV
      for (size_t ix = 0; ix < 3; ++ix) {
        scale(_hist_leptonpT_SR1[ix], norm*20.);
        scale(_hist_leptonpT_SR2[ix], norm*20.);
      }
      scale(_hist_etmiss_SR1_A, norm*20.);
      scale(_hist_etmiss_SR1_B, norm*20.);
      scale(_hist_etmiss_SR2_A, norm*20.);
      scale(_hist_etmiss_SR2_B, norm*20.);
      scale(_hist_mSFOS, norm*20.);
      // These are number of events at 2.06fb^-1
      scale(_count_SR1, norm);
      scale(_count_SR2, norm);
    }

    //@}


  private:

  /// @name Histograms
  //@{
  vector<Histo1DPtr> _hist_leptonpT_SR1, _hist_leptonpT_SR2;
  Histo1DPtr _hist_etmiss_SR1_A, _hist_etmiss_SR1_B, _hist_etmiss_SR2_A, _hist_etmiss_SR2_B;
  Histo1DPtr _hist_mSFOS, _count_SR1, _count_SR2;
  //@}

  };

  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2012_I1112263);

}