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ATLAS_2011_S9212183

0-lepton squark and gluino search
Experiment: ATLAS (LHC)
Inspire ID: 930002
Status: VALIDATED
Authors:
  • Chris Wymant
  • David Grellscheid
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • BSM signal events at 7000 GeV.

0-lepton search for squarks and gluinos by ATLAS at 7 TeV with an integrated luminosity of $1.04\,\mathrm{fb}^{-1}$. Event counts in five signal regions are implemented as one-bin histograms.

Source code: ATLAS_2011_S9212183.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/FastJets.hh"
  8
  9namespace Rivet {
 10
 11
 12  /// @brief 0-lepton squark and gluino search
 13  ///
 14  /// @author Chris Wymant
 15  class ATLAS_2011_S9212183 : public Analysis {
 16  public:
 17
 18    /// Constructor
 19    RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2011_S9212183);
 20
 21
 22    /// @name Analysis methods
 23    //@{
 24
 25    /// Book histograms and initialise projections before the run
 26    void init() {
 27
 28      // Projection to find the electrons
 29      IdentifiedFinalState elecs(Cuts::abseta < 2.47 && Cuts::pT > 20*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      declare(FastJets(FinalState(), FastJets::ANTIKT, 0.4), "AntiKtJets04");
 40
 41      // All tracks (to do deltaR with leptons)
 42      declare(ChargedFinalState(Cuts::abseta < 3.0), "cfs");
 43
 44      // Used for pTmiss (N.B. the real 'vfs' extends beyond 4.5 to |eta| = 4.9)
 45      declare(VisibleFinalState(Cuts::abseta < 4.5), "vfs");
 46
 47
 48      // Book histograms
 49      book(_count_2j   ,"count_2j",   1, 0., 1.);
 50      book(_count_3j   ,"count_3j",   1, 0., 1.);
 51      book(_count_4j5  ,"count_4j5",  1, 0., 1.);
 52      book(_count_4j10 ,"count_4j10", 1, 0., 1.);
 53      book(_count_HM   ,"count_HM",   1, 0., 1.);
 54
 55      book(_hist_meff_2j  ,1, 1, 1);
 56      book(_hist_meff_3j  ,2, 1, 1);
 57      book(_hist_meff_4j  ,3, 1, 1);
 58      book(_hist_meff_HM  ,4, 1, 1);
 59
 60      book(_hist_eTmiss  ,"Et_miss", 20, 0., 1000.);
 61    }
 62
 63
 64    /// Perform the per-event analysis
 65    void analyze(const Event& event) {
 66      const double weight = 1.0;
 67
 68      Jets cand_jets;
 69      const Jets jets = apply<FastJets>(event, "AntiKtJets04").jetsByPt(20.0*GeV);
 70      for (const Jet& jet : jets) {
 71        if ( fabs( jet.eta() ) < 4.9 ) {
 72          cand_jets.push_back(jet);
 73        }
 74      }
 75
 76      const Particles cand_e  = apply<IdentifiedFinalState>(event, "elecs").particlesByPt();
 77
 78      // Muon isolation not mentioned in hep-exp 1109.6572, unlike in 1102.5290,
 79      // but assumed to still be applicable
 80      Particles cand_mu;
 81      const Particles chg_tracks = apply<ChargedFinalState>(event, "cfs").particles();
 82      const Particles muons = apply<IdentifiedFinalState>(event, "muons").particlesByPt();
 83      for (const Particle& mu : muons) {
 84        double pTinCone = -mu.pT();
 85        for (const Particle& track : chg_tracks) {
 86          if ( deltaR(mu.momentum(),track.momentum()) <= 0.2 ) {
 87            pTinCone += track.pT();
 88          }
 89        }
 90        if ( pTinCone < 1.8*GeV ) cand_mu.push_back(mu);
 91      }
 92
 93      // Resolve jet-lepton overlap for jets with |eta| < 2.8
 94      Jets cand_jets_2;
 95      for ( const Jet& jet : cand_jets ) {
 96        if ( fabs( jet.eta() ) >= 2.8 ) {
 97          cand_jets_2.push_back( jet );
 98        } else {
 99          bool away_from_e = true;
100          for ( const Particle & e : cand_e ) {
101            if ( deltaR(e.momentum(),jet.momentum()) <= 0.2 ) {
102              away_from_e = false;
103              break;
104            }
105          }
106          if ( away_from_e ) cand_jets_2.push_back( jet );
107        }
108      }
109
110
111      Particles recon_e, recon_mu;
112
113      for ( const Particle & e : cand_e ) {
114        bool away = true;
115        for ( const Jet& jet : cand_jets_2 ) {
116          if ( deltaR(e.momentum(),jet.momentum()) < 0.4 ) {
117            away = false;
118            break;
119          }
120        }
121        if ( away ) recon_e.push_back( e );
122      }
123
124      for ( const Particle & mu : cand_mu ) {
125        bool away = true;
126        for ( const Jet& jet : cand_jets_2 ) {
127          if ( deltaR(mu.momentum(),jet.momentum()) < 0.4 ) {
128            away = false;
129            break;
130          }
131        }
132        if ( away ) recon_mu.push_back( mu );
133      }
134
135
136      // pTmiss
137      // Based on all candidate electrons, muons and jets, plus everything else with |eta| < 4.5
138      // i.e. everything in our projection "vfs" plus the jets with |eta| > 4.5
139      Particles vfs_particles = apply<VisibleFinalState>(event, "vfs").particles();
140      FourMomentum pTmiss;
141      for ( const Particle & p : vfs_particles ) {
142        pTmiss -= p.momentum();
143      }
144      for ( const Jet& jet : cand_jets_2 ) {
145        if ( fabs( jet.eta() ) > 4.5 ) pTmiss -= jet.momentum();
146      }
147      double eTmiss = pTmiss.pT();
148
149
150      // Final jet filter
151      Jets recon_jets;
152      for ( const Jet& jet : cand_jets_2 ) {
153        if ( fabs( jet.eta() ) <= 2.8 ) recon_jets.push_back( jet );
154      }
155      // NB. It seems that jets with |eta| > 2.8 could have been thrown away at
156      // the start; we don't do so, in order to follow both the structure of
157      // the paper and the similar Rivet analysis ATLAS_2011_S8983313
158
159      // 'candidate' muons needed only 10 GeV, to cause a veto they need 20 GeV
160      Particles veto_mu;
161      for ( const Particle & mu : cand_mu ) {
162        if ( mu.pT() >= 20.0*GeV ) veto_mu.push_back(mu);
163      }
164
165      if ( ! ( veto_mu.empty() && recon_e.empty() ) ) {
166        MSG_DEBUG("Charged leptons left after selection");
167        vetoEvent;
168      }
169
170      if ( eTmiss <= 130 * GeV ) {
171        MSG_DEBUG("Not enough eTmiss: " << eTmiss << " < 130");
172        vetoEvent;
173      }
174
175      if ( recon_jets.empty() || recon_jets[0].pT() <= 130.0 * GeV ) {
176        MSG_DEBUG("No hard leading jet in " << recon_jets.size() << " jets");
177        vetoEvent;
178      }
179
180      // ==================== observables ====================
181
182      int Njets = 0;
183      double min_dPhi = 999.999;
184      double pTmiss_phi = pTmiss.phi();
185      for ( const Jet& jet : recon_jets ) {
186        if ( jet.pT() > 40 * GeV ) {
187          if ( Njets < 3 ) {
188            min_dPhi = min( min_dPhi, deltaPhi( pTmiss_phi, jet.phi() ) );
189          }
190          ++Njets;
191        }
192      }
193
194      int NjetsHighMass = 0;
195      for ( const Jet& jet : recon_jets ) {
196        if ( jet.pT() > 80.0 * GeV ) {
197          ++NjetsHighMass;
198        }
199      }
200
201      if ( Njets < 2 ) {
202        MSG_DEBUG("Only " << Njets << " >40 GeV jets left");
203        vetoEvent;
204      }
205
206      if ( min_dPhi <= 0.4 ) {
207        MSG_DEBUG("dPhi too small");
208        vetoEvent;
209      }
210
211      // m_eff
212      double m_eff_2j = eTmiss + recon_jets[0].pT() + recon_jets[1].pT();
213      double m_eff_3j = recon_jets.size() < 3 ? -999.0 : m_eff_2j + recon_jets[2].pT();
214      double m_eff_4j = recon_jets.size() < 4 ? -999.0 : m_eff_3j + recon_jets[3].pT();
215      double m_eff_HM = eTmiss;
216      for ( const Jet& jet : recon_jets ) {
217        if ( jet.pT() > 40.0 * GeV ) m_eff_HM += jet.pT();
218      }
219
220      double et_meff_2j = eTmiss / m_eff_2j;
221      double et_meff_3j = eTmiss / m_eff_3j;
222      double et_meff_4j = eTmiss / m_eff_4j;
223      double et_meff_HM = eTmiss / m_eff_HM;
224
225
226      // ==================== FILL ====================
227
228      MSG_DEBUG( "Trying to fill "
229                 << Njets << ' '
230                 << m_eff_2j << ' '
231                 << et_meff_2j << ' '
232                 << m_eff_3j << ' '
233                 << et_meff_3j << ' '
234                 << m_eff_4j << ' '
235                 << et_meff_4j << ' '
236                 << m_eff_HM << ' '
237                 << et_meff_HM );
238
239
240      _hist_eTmiss->fill(eTmiss, weight);
241
242
243      // 2j region
244      if ( et_meff_2j > 0.3 ) {
245        _hist_meff_2j->fill(m_eff_2j, weight);
246        if ( m_eff_2j > 1000 * GeV ) {
247          MSG_DEBUG("Hits 2j");
248          _count_2j->fill(0.5, weight);
249        }
250      }
251
252
253      // 3j region
254      if ( Njets >= 3 && et_meff_3j > 0.25 ) {
255        _hist_meff_3j->fill(m_eff_3j, weight);
256        if ( m_eff_3j > 1000 * GeV ) {
257          MSG_DEBUG("Hits 3j");
258          _count_3j->fill(0.5, weight);
259        }
260      }
261
262
263      // 4j5 & 4j10 regions
264      if ( Njets >= 4 && et_meff_4j > 0.25 ) {
265        _hist_meff_4j->fill(m_eff_4j, weight);
266        if ( m_eff_4j > 500 * GeV ) {
267          MSG_DEBUG("Hits 4j5");
268          _count_4j5->fill(0.5, weight);
269        }
270        if ( m_eff_4j > 1000 * GeV ) {
271          MSG_DEBUG("Hits 4j10");
272          _count_4j10->fill(0.5, weight);
273        }
274      }
275
276
277      // High mass region
278      if ( NjetsHighMass >= 4 && et_meff_HM > 0.2 ) {
279        _hist_meff_HM->fill(m_eff_HM, weight);
280        if ( m_eff_HM > 1100 * GeV ) {
281          MSG_DEBUG("Hits HM");
282          _count_HM->fill(0.5, weight);
283        }
284      }
285
286    }
287
288
289    void finalize() {
290      // Two, three and four jet channels have bin width = 100 (GeV)
291      // High mass channel has bin width = 150 (GeV)
292      // Integrated luminosity = 1040 (pb)
293      scale( _hist_meff_2j, 100. * 1040 * crossSection()/sumOfWeights() );
294      scale( _hist_meff_3j, 100. * 1040 * crossSection()/sumOfWeights() );
295      scale( _hist_meff_4j, 100. * 1040 * crossSection()/sumOfWeights() );
296      scale( _hist_meff_HM, 150. * 1040 * crossSection()/sumOfWeights() );
297    }
298
299    //@}
300
301
302  private:
303
304    Histo1DPtr _count_2j;
305    Histo1DPtr _count_3j;
306    Histo1DPtr _count_4j5;
307    Histo1DPtr _count_4j10;
308    Histo1DPtr _count_HM;
309    Histo1DPtr _hist_meff_2j;
310    Histo1DPtr _hist_meff_3j;
311    Histo1DPtr _hist_meff_4j;
312    Histo1DPtr _hist_meff_HM;
313    Histo1DPtr _hist_eTmiss;
314
315  };
316
317
318  RIVET_DECLARE_ALIASED_PLUGIN(ATLAS_2011_S9212183, ATLAS_2011_I930002);
319
320}