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ATLAS_2011_CONF_2011_090

Single lepton search for supersymmetry
Experiment: ATLAS (LHC)
Status: OBSOLETE
Authors:
  • Angela Chen
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • BSM signal events at 7000 GeV.

Single lepton search for supersymmmetric particles by ATLAS at 7 TeV. Event counts in electron and muon signal regions are implemented as one-bin histograms. Histograms for missing transverse energy and effective mass are implemented for the two signal regions.

Source code: ATLAS_2011_CONF_2011_090.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_2011_CONF_2011_090 : public Analysis {
 14  public:
 15
 16    /// @name Constructors etc.
 17    /// @{
 18
 19    /// Constructor
 20
 21    ATLAS_2011_CONF_2011_090()
 22      : Analysis("ATLAS_2011_CONF_2011_090")
 23    {    }
 24
 25    /// @}
 26
 27
 28  public:
 29
 30    /// @name Analysis methods
 31    /// @{
 32
 33    /// Book histograms and initialize projections before the run
 34    void init() {
 35
 36      // projection to find the electrons
 37      IdentifiedFinalState elecs(Cuts::abseta < 2.47 && Cuts::pT >= 20*GeV);
 38      elecs.acceptIdPair(PID::ELECTRON);
 39      declare(elecs, "elecs");
 40
 41      // veto region electrons (from 2010 arXiv:1102.2357v2)
 42      Cut vetocut = Cuts::absetaIn(1.37, 1.52);
 43      IdentifiedFinalState veto_elecs(vetocut && Cuts::pT > 10*GeV);
 44      veto_elecs.acceptIdPair(PID::ELECTRON);
 45      declare(veto_elecs, "veto_elecs");
 46
 47      // projection to find the muons
 48      IdentifiedFinalState muons(Cuts::abseta < 2.4 && Cuts::pT > 10*GeV);
 49      muons.acceptIdPair(PID::MUON);
 50      declare(muons, "muons");
 51
 52      // Jet finder
 53      VetoedFinalState vfs;
 54      vfs.addVetoPairId(PID::MUON);
 55      declare(FastJets(vfs, JetAlg::ANTIKT, 0.4), "AntiKtJets04");
 56
 57      // all tracks (to do deltaR with leptons)
 58      declare(ChargedFinalState(Cuts::abseta < 3.0 && Cuts::pT > 0.5*GeV), "cfs");
 59
 60      // for pTmiss
 61      declare(VisibleFinalState(Cuts::abseta < 4.9), "vfs");
 62
 63      /// Book histograms
 64      book(_count_mu_channel ,"count_muon_channel", 1, 0., 1.);
 65      book(_count_e_channel ,"count_electron_channel", 1, 0., 1.);
 66      book(_hist_eTmiss_e ,"Et_miss_e", 50, 0., 500.);
 67      book(_hist_eTmiss_mu ,"Et_miss_mu", 50, 0., 500.);
 68      book(_hist_m_eff_e ,"m_eff_e", 60, 0., 1500.);
 69      book(_hist_m_eff_mu ,"m_eff_mu", 60, 0., 1500.);
 70      book(_hist_m_eff_e_final ,"m_eff_e_final", 15, 0., 1500.);
 71      book(_hist_m_eff_mu_final ,"m_eff_mu_final", 15, 0., 1500.);
 72    }
 73
 74
 75
 76    /// Perform the per-event analysis
 77    void analyze(const Event& event) {
 78
 79
 80      Particles veto_e = apply<IdentifiedFinalState>(event, "veto_elecs").particles();
 81      if ( ! veto_e.empty() ) {
 82        MSG_DEBUG("electrons in veto region");
 83        vetoEvent;
 84      }
 85
 86      Jets cand_jets = apply<FastJets>(event, "AntiKtJets04").jetsByPt(Cuts::pT > 20*GeV && Cuts::abseta < 2.8);
 87
 88      Particles candtemp_e = apply<IdentifiedFinalState>(event, "elecs").particlesByPt();
 89      Particles candtemp_mu = apply<IdentifiedFinalState>(event,"muons").particlesByPt();
 90      Particles chg_tracks = apply<ChargedFinalState>(event, "cfs").particles();
 91      Particles cand_mu;
 92      Particles cand_e;
 93
 94      // pTcone around muon track
 95      for ( const Particle& mu : candtemp_mu ) {
 96        double pTinCone = -mu.pT();
 97        for ( const Particle& track : chg_tracks ) {
 98          if ( deltaR(mu, track) < 0.2 )
 99            pTinCone += track.pT();
100        }
101        if ( pTinCone < 1.8*GeV )
102          cand_mu.push_back(mu);
103      }
104
105
106      // pTcone around electron
107      for ( const Particle& e : candtemp_e ) {
108        double pTinCone = -e.pT();
109        for ( const Particle& track : chg_tracks ) {
110          if ( deltaR(e, track) < 0.2 )
111            pTinCone += track.pT();
112        }
113        if ( pTinCone < 0.10 * e.pT() )
114          cand_e.push_back(e);
115      }
116
117
118      // discard jets that overlap with electrons
119      Jets cand_jets_2;
120      for ( const Jet& jet : cand_jets ) {
121        bool away_from_e = true;
122        for ( const Particle & e : cand_e ) {
123          if ( deltaR(e, jet) <= 0.2 ) {
124            away_from_e = false;
125            break;
126          }
127        }
128        if ( away_from_e )
129          cand_jets_2.push_back( jet );
130      }
131
132      // only consider leptons far from jet
133      Particles recon_e, recon_mu;
134      for ( const Particle & e : cand_e ) {
135        bool e_near_jet = false;
136        for ( const Jet& jet : cand_jets_2 ) {
137          if (inRange(deltaR(e, jet), 0.2, 0.4)) e_near_jet = true;
138        }
139        if ( ! e_near_jet ) recon_e.push_back( e );
140      }
141
142      for ( const Particle & mu : cand_mu ) {
143        bool mu_near_jet = false;
144        for ( const Jet& jet : cand_jets_2 ) {
145          if ( deltaR(mu, jet) < 0.4 ) mu_near_jet = true;
146        }
147        if ( ! mu_near_jet ) recon_mu.push_back( mu );
148      }
149
150      // pTmiss
151      Particles vfs_particles
152        = apply<VisibleFinalState>(event, "vfs").particles();
153      FourMomentum pTmiss;
154      for ( const Particle & p : vfs_particles ) {
155        pTmiss -= p.momentum();
156      }
157      double eTmiss = pTmiss.pT();
158
159
160      // final jet filter
161      Jets recon_jets;
162      for ( const Jet& jet : cand_jets_2 ) {
163        recon_jets.push_back( jet );
164      }
165
166
167
168
169      // ==================== observables ====================
170
171
172      // Njets
173
174      int Njets = 0;
175      double pTmiss_phi = pTmiss.phi();
176      for ( const Jet& jet : recon_jets ) {
177        if ( jet.abseta() < 2.8 )
178          Njets+=1;
179      }
180      if ( Njets < 3 ) {
181        MSG_DEBUG("Only " << Njets << " jets w/ eta<2.8 left");
182        vetoEvent;
183      }
184
185      if ( recon_jets[0].pT() <= 60.0 * GeV ) {
186        MSG_DEBUG("No hard leading jet in " << recon_jets.size() << " jets");
187        vetoEvent;
188      }
189      for ( int i = 1; i < 3; ++i ) {
190        if ( recon_jets[i].pT() <= 25*GeV ) {
191          vetoEvent;
192        }
193      }
194
195      for ( int i = 0; i < 3; ++i ) {
196        double dPhi = deltaPhi( pTmiss_phi, recon_jets[i].phi() );
197        if ( dPhi <= 0.2 ) {
198          MSG_DEBUG("dPhi too small");
199          vetoEvent;
200          break;
201        }
202      }
203
204
205      Particles lepton;
206      if ( recon_mu.empty() && recon_e.empty() ) {
207        MSG_DEBUG("No leptons");
208        vetoEvent;
209      }
210      else {
211        for ( const Particle & mu : recon_mu )
212          lepton.push_back(mu);
213        for ( const Particle & e : recon_e )
214          lepton.push_back(e);
215      }
216
217      std::sort(lepton.begin(), lepton.end(), cmpMomByPt);
218
219      double e_id = 11;
220      double mu_id = 13;
221
222      // one hard leading lepton cut
223      if ( lepton[0].abspid() == e_id &&
224           lepton[0].pT() <= 25*GeV ) {
225        vetoEvent;
226      }
227      else if ( lepton[0].abspid() == mu_id &&
228                lepton[0].pT() <= 20*GeV ) {
229        vetoEvent;
230      }
231
232      // exactly one hard leading lepton cut
233      if(lepton.size()>1) {
234        if ( lepton[1].abspid() == e_id &&
235             lepton[1].pT() > 20*GeV ) {
236          vetoEvent;
237        }
238        else if ( lepton[1].abspid() == mu_id &&
239                  lepton[1].pT() > 10*GeV ) {
240          vetoEvent;
241        }
242      }
243
244
245      // ==================== FILL ====================
246
247
248      FourMomentum pT_l = lepton[0].momentum();
249
250
251      double dPhi = deltaPhi( pT_l.phi(), pTmiss_phi);
252      double mT = sqrt( 2 * pT_l.pT() * eTmiss * (1 - cos(dPhi)) );
253
254
255      // effective mass
256      double m_eff = eTmiss + pT_l.pT()
257        + recon_jets[0].pT()
258        + recon_jets[1].pT()
259        + recon_jets[2].pT();
260
261
262      // Electron channel signal region
263
264      if (  lepton[0].abspid() == e_id ) {
265
266        _hist_eTmiss_e->fill(eTmiss);
267        _hist_m_eff_e->fill(m_eff);
268
269        if ( mT > 100*GeV && eTmiss > 125*GeV ) {
270          _hist_m_eff_e_final->fill(m_eff);
271          if ( m_eff > 500*GeV && eTmiss > 0.25*m_eff ) {
272            _count_e_channel->fill(0.5);
273          }
274        }
275      }
276
277      // Muon channel signal region
278
279      else if (  lepton[0].abspid() == mu_id ) {
280
281        _hist_eTmiss_mu->fill(eTmiss);
282        _hist_m_eff_mu->fill(m_eff);
283
284        if ( mT > 100*GeV && eTmiss > 125*GeV ) {
285          _hist_m_eff_mu_final->fill(m_eff);
286          if ( m_eff > 500*GeV && eTmiss > 0.25*m_eff ) {
287            _count_mu_channel->fill(0.5);
288          }
289        }
290
291      }
292
293
294    }
295
296    /// @}
297
298
299    void finalize() {
300      scale( _hist_eTmiss_e      , 10.  * 165. * crossSection()/picobarn/sumOfWeights() );
301      scale( _hist_eTmiss_mu     , 10.  * 165. * crossSection()/picobarn/sumOfWeights() );
302      scale( _hist_m_eff_e       , 25.  * 165. * crossSection()/picobarn/sumOfWeights() );
303      scale( _hist_m_eff_mu      , 25.  * 165. * crossSection()/picobarn/sumOfWeights() );
304      scale( _hist_m_eff_e_final , 100. * 165. * crossSection()/picobarn/sumOfWeights() );
305      scale( _hist_m_eff_mu_final, 100. * 165. * crossSection()/picobarn/sumOfWeights() );
306    }
307
308  private:
309
310    /// @name Histograms
311    /// @{
312    Histo1DPtr _count_e_channel;
313    Histo1DPtr _count_mu_channel;
314
315    Histo1DPtr _hist_eTmiss_e;
316    Histo1DPtr _hist_eTmiss_mu;
317
318    Histo1DPtr _hist_m_eff_e;
319    Histo1DPtr _hist_m_eff_mu;
320    Histo1DPtr _hist_m_eff_e_final;
321    Histo1DPtr _hist_m_eff_mu_final;
322
323
324    /// @}
325
326
327  };
328
329
330
331  RIVET_DECLARE_PLUGIN(ATLAS_2011_CONF_2011_090);
332
333}