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ATLAS_2012_CONF_2012_104

Search for supersymmetry at 8 TeV with jets, missing transverse momentum and one lepton
Experiment: ATLAS (LHC)
Status: OBSOLETE
Authors:
  • Peter Richardson
References:
  • ATLAS-CONF-2012-104
Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • BSM signal events at 8000 GeV.

One lepton search for supersymmmetric particles by ATLAS at 8 TeV with $5.8\,\text{fb}^{-1}$ integrated luminosity. Event counts in the signal regions are implemented as one-bin histograms. Histograms for effective mass are implemented for the two signal hard lepton signal regions and the ratio of missing transverse energy to effective mass for the soft lepton region.

Source code: ATLAS_2012_CONF_2012_104.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/ChargedFinalState.hh"
  5#include "Rivet/Projections/VisibleFinalState.hh"
  6#include "Rivet/Projections/IdentifiedFinalState.hh"
  7#include "Rivet/Projections/VetoedFinalState.hh"
  8#include "Rivet/Projections/FastJets.hh"
  9
 10namespace Rivet {
 11
 12
 13  class ATLAS_2012_CONF_2012_104 : public Analysis {
 14  public:
 15
 16    /// Constructor
 17    ATLAS_2012_CONF_2012_104()
 18      : Analysis("ATLAS_2012_CONF_2012_104")
 19    {    }
 20
 21
 22    /// @name Analysis methods
 23    //@{
 24
 25    /// Book histograms and initialize projections before the run
 26    void init() {
 27
 28      // projection to find the electrons
 29      IdentifiedFinalState elecs(Cuts::abseta < 2.47 && Cuts::pT > 10*GeV);
 30      elecs.acceptIdPair(PID::ELECTRON);
 31      declare(elecs, "elecs");
 32
 33      // projection to find the muons
 34      IdentifiedFinalState muons(Cuts::abseta < 2.4 && Cuts::pT > 10*GeV);
 35      muons.acceptIdPair(PID::MUON);
 36      declare(muons, "muons");
 37
 38      // Jet finder
 39      VetoedFinalState vfs;
 40      vfs.addVetoPairId(PID::MUON);
 41      declare(FastJets(vfs, FastJets::ANTIKT, 0.4), "AntiKtJets04");
 42
 43      // all tracks (to do deltaR with leptons)
 44      declare(ChargedFinalState(Cuts::abseta < 3 && Cuts::pT > 0.5*GeV), "cfs");
 45
 46      // for pTmiss
 47      declare(VisibleFinalState(Cuts::abseta < 4.9),"vfs");
 48
 49      // Book histograms
 50      book(_count_e  ,"count_e" , 1, 0., 1.);
 51      book(_count_mu ,"count_mu", 1, 0., 1.);
 52
 53      book(_hist_eTmiss_e  ,"hist_eTmiss_e"  , 25, 0., 1000.);
 54      book(_hist_eTmiss_mu ,"hist_eTmiss_mu" , 25, 0., 1000.);
 55
 56    }
 57
 58    /// Perform the per-event analysis
 59    void analyze(const Event& event) {
 60      const double weight = 1.0;
 61
 62      // get the candiate jets
 63      Jets cand_jets;
 64      for ( const Jet& jet :
 65                apply<FastJets>(event, "AntiKtJets04").jetsByPt(20.0*GeV) ) {
 66        if ( fabs( jet.eta() ) < 2.8 ) {
 67          cand_jets.push_back(jet);
 68        }
 69      }
 70
 71      // get the candidate "medium" leptons without isolation
 72      Particles cand_e;
 73      for( const Particle & e :
 74               apply<IdentifiedFinalState>(event, "elecs").particlesByPt()) {
 75        // remove any leptons within 0.4 of any candidate jets
 76        bool e_near_jet = false;
 77        for ( const Jet& jet : cand_jets ) {
 78          double dR = deltaR(e.momentum(),jet.momentum());
 79          if ( dR < 0.4 && dR > 0.2 ) {
 80            e_near_jet = true;
 81            break;
 82          }
 83        }
 84        if ( ! e_near_jet ) cand_e.push_back(e);
 85      }
 86      Particles cand_mu;
 87      for( const Particle & mu :
 88               apply<IdentifiedFinalState>(event, "muons").particlesByPt()) {
 89        // remove any leptons within 0.4 of any candidate jets
 90        bool mu_near_jet = false;
 91        for ( const Jet& jet : cand_jets ) {
 92          if ( deltaR(mu.momentum(),jet.momentum()) < 0.4 ) {
 93            mu_near_jet = true;
 94            break;
 95          }
 96        }
 97        if ( ! mu_near_jet ) cand_mu.push_back(mu);
 98      }
 99      // apply the isolation
100      Particles chg_tracks =
101        apply<ChargedFinalState>(event, "cfs").particles();
102      // pTcone around muon track (hard)
103      Particles recon_mu;
104      for ( const Particle & mu : cand_mu ) {
105        double pTinCone = -mu.pT();
106        if(-pTinCone<25.) continue;
107        for ( const Particle & track : chg_tracks ) {
108          if ( deltaR(mu.momentum(),track.momentum()) < 0.2 )
109            pTinCone += track.pT();
110        }
111        if ( pTinCone < 1.8*GeV ) recon_mu.push_back(mu);
112      }
113      // pTcone around electron track (hard)
114      Particles recon_e;
115      for ( const Particle & e : cand_e ) {
116        double pTinCone = -e.pT();
117        if(-pTinCone<25.) continue;
118        for ( const Particle & track : chg_tracks ) {
119          if ( deltaR(e.momentum(),track.momentum()) < 0.2 )
120            pTinCone += track.pT();
121        }
122        if ( pTinCone < 0.1 * e.pT() ) recon_e.push_back(e);
123      }
124
125      // discard jets that overlap with electrons
126      Jets recon_jets;
127      for ( const Jet& jet : cand_jets ) {
128        if(jet.abseta()>2.5||
129           jet.perp()<25.) continue;
130        bool away_from_e = true;
131        for ( const Particle & e : cand_e ) {
132          if ( deltaR(e.momentum(),jet.momentum()) < 0.2 ) {
133            away_from_e = false;
134            break;
135          }
136        }
137        if ( away_from_e ) recon_jets.push_back( jet );
138      }
139
140      // pTmiss
141      FourMomentum pTmiss;
142      for ( const Particle & p :
143                apply<VisibleFinalState>(event, "vfs").particles() ) {
144        pTmiss -= p.momentum();
145      }
146      double eTmiss = pTmiss.pT();
147
148      // at least 4 jets with pT>80.
149      if(recon_jets.size()<4 || recon_jets[3].perp()<80.) vetoEvent;
150
151      // only 1 signal lepton
152      if( recon_e.size() + recon_mu.size() != 1 )
153        vetoEvent;
154      if( cand_e .size() + cand_mu .size() != 1 )
155        vetoEvent;
156
157      // start of meff calculation
158      double HT=0.;
159      for( const Jet & jet : recon_jets) {
160        double pT = jet.perp();
161        if(pT>40.) HT += pT;
162      }
163
164      // get the lepton
165      Particle lepton = recon_e.empty() ? recon_mu[0] : recon_e[0];
166
167      // lepton variables
168      double pT = lepton.perp();
169
170      double mT  = 2.*(pT*eTmiss -
171                       lepton.px()*pTmiss.px() -
172                       lepton.py()*pTmiss.py());
173      mT = sqrt(mT);
174      HT += pT;
175      double m_eff_inc  = HT + eTmiss + pT;
176      double m_eff_4 = eTmiss + pT;
177      for(unsigned int ix=0;ix<4;++ix)
178        m_eff_4 +=  recon_jets[ix].perp();
179
180      // four jet selecton
181      if(mT>100.&& eTmiss/m_eff_4>0.2 &&
182         m_eff_inc > 800.) {
183        if( eTmiss > 250. ) {
184          if(lepton.abspid()==PID::ELECTRON)
185            _count_e->fill(0.5,weight);
186          else if(lepton.abspid()==PID::MUON)
187            _count_mu->fill(0.5,weight);
188        }
189        if(lepton.abspid()==PID::ELECTRON)
190          _hist_eTmiss_e ->fill(eTmiss,weight);
191        else if(lepton.abspid()==PID::MUON)
192          _hist_eTmiss_mu->fill(eTmiss,weight);
193      }
194    }
195    //@}
196
197
198    void finalize() {
199
200      double norm = 5.8* crossSection()/sumOfWeights()/femtobarn;
201      scale(_count_e ,norm);
202      scale(_count_mu,norm);
203      scale(_hist_eTmiss_e  ,40.*norm);
204      scale(_hist_eTmiss_mu ,40.*norm);
205
206    }
207
208  private:
209
210    /// @name Histograms
211    //@{
212    Histo1DPtr _count_e ;
213    Histo1DPtr _count_mu;
214
215    Histo1DPtr _hist_eTmiss_e ;
216    Histo1DPtr _hist_eTmiss_mu;
217    //@}
218
219  };
220
221  // The hook for the plugin system
222  RIVET_DECLARE_PLUGIN(ATLAS_2012_CONF_2012_104);
223
224}