ATLAS_2012_I1126136.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/IdentifiedFinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Tools/RivetMT2.hh"

namespace Rivet {


  class ATLAS_2012_I1126136 : public Analysis {
  public:

    /// @name Constructors etc.
    //@{

    /// Constructor

    ATLAS_2012_I1126136()
      : Analysis("ATLAS_2012_I1126136")
    {    }

    //@}


  public:

    /// @name Analysis methods
    //@{

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

      // projection to find the electrons
      vector<pair<double, double> > eta_e;
      eta_e.push_back(make_pair(-2.47,2.47));
      IdentifiedFinalState elecs(eta_e, 20.0*GeV);
      elecs.acceptIdPair(PID::ELECTRON);
      addProjection(elecs, "elecs");

      // projection to find the muons
      vector<pair<double, double> > eta_m;
      eta_m.push_back(make_pair(-2.4,2.4));
      IdentifiedFinalState muons(eta_m, 10.0*GeV);
      muons.acceptIdPair(PID::MUON);
      addProjection(muons, "muons");

      // Jet finder
      VetoedFinalState vfs;
      vfs.addVetoPairId(PID::MUON);
      addProjection(FastJets(vfs, FastJets::ANTIKT, 0.4),
            "AntiKtJets04");

      // for pTmiss
      addProjection(VisibleFinalState(-4.9,4.9),"vfs");

      // Book histograms
      _count_SR_A     = bookHisto1D("count_SR_A"    , 1, 0., 1.);
      _count_SR_B     = bookHisto1D("count_SR_B"    , 1, 0., 1.);

      _hist_mjjj1  = bookHisto1D("hist_mjjj1" , 30 , 0.   , 600.  );
      _hist_mjjj2  = bookHisto1D("hist_mjjj2" , 30 , 0.   , 600.  );
      _hist_ETmiss = bookHisto1D("hist_ETmiss", 20 , 100. , 600.  );
      _hist_mT2    = bookHisto1D("hist_mT2"   , 200, 0.   , 1000. );

    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const double weight = event.weight();

      // pTmiss
      FourMomentum pTmiss;
      foreach ( const Particle & p,
                applyProjection<VisibleFinalState>(event, "vfs").particles() ) {
        pTmiss -= p.momentum();
      }
      double ETmiss = pTmiss.perp();

      // require eTmiss > 150
      if(ETmiss<150.) vetoEvent;

      // get the candiate jets
      Jets cand_jets;
      foreach ( const Jet& jet,
                applyProjection<FastJets>(event, "AntiKtJets04").jetsByPt(20.0*GeV) ) {
        if ( fabs( jet.eta() ) < 4.5 ) {
          cand_jets.push_back(jet);
        }
      }

      // find the electrons
      Particles cand_e;
      foreach( const Particle & e,
               applyProjection<IdentifiedFinalState>(event, "elecs").particlesByPt()) {
        // remove any leptons within 0.4 of any candidate jets
        bool e_near_jet = false;
        foreach ( const Jet& jet, cand_jets ) {
          double dR = deltaR(e.momentum(),jet.momentum());
          if ( dR < 0.4 && dR > 0.2 ) {
            e_near_jet = true;
            break;
          }
        }
        if ( e_near_jet ) continue;
        cand_e.push_back(e);
      }

      // find the muons
      Particles cand_mu;
      foreach( const Particle & mu,
               applyProjection<IdentifiedFinalState>(event, "muons").particlesByPt()) {
        // remove any leptons within 0.4 of any candidate jets
        bool mu_near_jet = false;
        foreach ( const Jet& jet, cand_jets ) {
          if ( deltaR(mu.momentum(),jet.momentum()) < 0.4 ) {
            mu_near_jet = true;
            break;
          }
        }
        if ( mu_near_jet ) continue;
        cand_mu.push_back(mu);
      }

      // veto events with leptons
      if( ! cand_e.empty() || ! cand_mu.empty() )
    vetoEvent;

      // discard jets that overlap with electrons
      Jets recon_jets;
      foreach ( const Jet& jet, cand_jets ) {
        if(fabs(jet.eta())>2.8 ||
           jet.momentum().perp()<30.) continue;
        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 );
      }

      // find b jets
      Jets tight_bjets,loose_bjets;
      foreach(const Jet & jet, recon_jets) {
    if(!jet.containsBottom() && jet.eta()>2.5) continue;
    double prob = rand()/static_cast<double>(RAND_MAX);
    if(prob <= 0.60) tight_bjets.push_back(jet);
    if(prob <= 0.75) loose_bjets.push_back(jet);
      }

      // require >=1 tight or >=2 loose b-jets
      if( ! ( !tight_bjets.empty() || loose_bjets.size()>=2) )
    vetoEvent;

      // must be at least 6 jets with pT>30
      if(recon_jets.size()<6 ) vetoEvent;

      // hardest > 130
      if(recon_jets[0].momentum().perp() < 130. ) vetoEvent;

      // three hardest jets must be separated from etmiss
      for(unsigned int ix=0;ix<3;++ix) {
    if(deltaPhi(recon_jets[ix].momentum(),pTmiss)<0.2*PI)
      vetoEvent;
      }

      // remove events with tau like jets
      for(unsigned int ix=3;ix<recon_jets.size();++ix) {
    // skip jets seperated from eTmiss
    if(deltaPhi(recon_jets[ix].momentum(),pTmiss)>=0.2*PI)
      continue;
    // check the number of tracks between 1 and 4
    unsigned int ncharged=0;
    foreach ( const Particle & particle, recon_jets[ix].particles()) {
      if(PID::threeCharge(particle.pdgId())!=0) ++ncharged;
    }
    if(ncharged==0 || ncharged>4) continue;
    // calculate transverse mass and reject if < 100
    double mT = 2.*recon_jets[ix].momentum().perp()*ETmiss
      -recon_jets[ix].momentum().x()*pTmiss.x()
      -recon_jets[ix].momentum().y()*pTmiss.y();
    if(mT<100.) vetoEvent;
      }

      // if 2 loose b-jets apply mT cut
      if(loose_bjets.size()>=2) {
    // find b-jet closest to eTmiss
    double minR(1e30);
    unsigned int ijet(0);
    for(unsigned int ix=0;ix<loose_bjets.size();++ix) {
      double dR = deltaR(loose_bjets[ix].momentum(),pTmiss);
      if(dR<minR) {
        minR=dR;
        ijet = ix;
      }
    }
    double  mT = 2.*loose_bjets[ijet].momentum().perp()*ETmiss
      -loose_bjets[ijet].momentum().x()*pTmiss.x()
      -loose_bjets[ijet].momentum().y()*pTmiss.y();
    if(mT<170.) vetoEvent;
      }

      // 1 tight b-jet apply mT cut
      if(tight_bjets.size()==1) {
    for(unsigned int ix=0;ix<4;++ix) {
      double mT = 2.*recon_jets[ix].momentum().perp()*ETmiss
        -recon_jets[ix].momentum().x()*pTmiss.x()
        -recon_jets[ix].momentum().y()*pTmiss.y();
      if(mT<175.) vetoEvent;
    }
      }

      // find the closest triplet of jets in (eta,phi)
      unsigned int j1(0),j2(0),j3(0);
      double minR2(1e30);
      for(unsigned int i1=0;i1<recon_jets.size();++i1) {
    for(unsigned int i2=i1+1;i2<recon_jets.size();++i2) {
      for(unsigned int i3=i2+1;i3<recon_jets.size();++i3) {
        double delR2 =
          sqr(deltaR(recon_jets[i1].momentum(),recon_jets[i2].momentum())) +
          sqr(deltaR(recon_jets[i1].momentum(),recon_jets[i3].momentum())) +
          sqr(deltaR(recon_jets[i2].momentum(),recon_jets[i3].momentum()));
        if(delR2<minR2) {
          minR2=delR2;
          j1=i1;
          j2=i2;
          j3=i3;
        }
      }
    }
      }
      // 4-momentum and mass of first triplet
      FourMomentum pjjj1 = recon_jets[j1].momentum() +
    recon_jets[j2].momentum()+ recon_jets[j3].momentum();
      double mjjj1 = pjjj1.mass();

      // find the second triplet
      unsigned int j4(0),j5(0),j6(0);
      minR2=0.;
      for(unsigned int i1=0;i1<recon_jets.size();++i1) {
    if(i1==j1||i1==j2||i1==j3) continue;
    for(unsigned int i2=i1+1;i2<recon_jets.size();++i2) {
      if(i2==j1||i2==j2||i2==j3) continue;
      for(unsigned int i3=i2+1;i3<recon_jets.size();++i3) {
        if(i3==j1||i3==j2||i3==j3) continue;
        double delR2 =
          sqr(deltaR(recon_jets[i1].momentum(),recon_jets[i2].momentum())) +
          sqr(deltaR(recon_jets[i1].momentum(),recon_jets[i3].momentum())) +
          sqr(deltaR(recon_jets[i2].momentum(),recon_jets[i3].momentum()));
        if(delR2<minR2) {
          minR2=delR2;
          j4=i1;
          j5=i2;
          j6=i3;
        }
      }
    }
      }

      // 4-momentum and mass of first triplet
      FourMomentum pjjj2 = recon_jets[j4].momentum() +
    recon_jets[j5].momentum()+ recon_jets[j6].momentum();
      double mjjj2 = pjjj2.mass();

      _hist_mjjj1->fill(mjjj1,weight);
      _hist_mjjj2->fill(mjjj2,weight);
      // require triplets in 80<mjjj<270
      if(mjjj1<80.||mjjj1>270.||mjjj2<80.||mjjj2>270.)
    vetoEvent;

      // counts in signal regions
      _count_SR_A->fill(0.5,weight);
      if(ETmiss>260.) _count_SR_B->fill(0.5,weight);

      _hist_ETmiss->fill(ETmiss,weight);
      double m_T2 = mT2::mT2( pjjj1,pjjj2,
                  pTmiss,0.0 ); // zero mass invisibles
      _hist_mT2->fill(m_T2,weight);
    }
    //@}


    void finalize() {

      double norm = 4.7* crossSection()/sumOfWeights()/femtobarn;
      scale(_count_SR_A ,     norm );
      scale(_count_SR_B ,     norm );
      scale(_hist_mjjj1 , 20.*norm );
      scale(_hist_ETmiss, 50.*norm );
      scale(_hist_mjjj2 , 20.*norm );
      scale(_hist_mT2   ,     norm );

    }

  private:

    /// @name Histograms
    //@{
    Histo1DPtr _count_SR_A;
    Histo1DPtr _count_SR_B;

    Histo1DPtr _hist_mjjj1;
    Histo1DPtr _hist_mjjj2;
    Histo1DPtr _hist_ETmiss;
    Histo1DPtr _hist_mT2;
    //@}

  };

  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2012_I1126136);

}