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CMS_2018_I1662081

Measurement of the differential cross sections of top quark pair production as a function of kinematic event variables in pp collisions at sqrt(s) = 13 TeV
Experiment: CMS (LHC)
Inspire ID: 1662081
Status: VALIDATED
Authors:
  • Doug Burns
  • Emyr Clement
  • Markus Seidel
References:
  • TOP-16-014
  • arxiv:1803.03991
  • Submitted to JHEP
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • ttbar events at sqrt(s) = 13 TeV, lepton+jets selection at particle level

Abstract : Measurements of the differential t¯t production cross section are presented in the single-lepton decay channel, with respect to a number of global event observables. The measurements are performed with 35.9 fb1 of proton-proton collision data collected by the CMS experiment at the LHC during 2016 at s=13 TeV. The differential cross sections are measured at the level of long-lived generated particles in a phase space similar to that accessible by the CMS detector, and are compared to state-of-the-art leading-order and next-to-leading-order t¯t simulations. Rivet : This analysis is to be run on tˉt simulation. The particle level selection requires: - exactly one electron or muon with pT>26 GeV and |η|<2.4 - no additional electrons or muons with pT>15 GeV and |η|<2.4 - at least three jets with pT>30 GeV and |η|<2.4, and one jet with pT>25 GeV and |η|<2.4 - two of these selected jets must be tagged as originating from a b quark.

Source code: CMS_2018_I1662081.cc
  1#include "Rivet/Analysis.hh"
  2#include "Rivet/Projections/FinalState.hh"
  3#include "Rivet/Projections/FastJets.hh"
  4#include "Rivet/Projections/ChargedLeptons.hh"
  5#include "Rivet/Projections/LeptonFinder.hh"
  6#include "Rivet/Projections/IdentifiedFinalState.hh"
  7#include "Rivet/Projections/PromptFinalState.hh"
  8#include "Rivet/Projections/VetoedFinalState.hh"
  9#include "Rivet/Projections/MissingMomentum.hh"
 10
 11namespace Rivet {
 12
 13
 14  class CMS_2018_I1662081 : public Analysis {
 15  public:
 16
 17    // Minimal constructor
 18    CMS_2018_I1662081()
 19      : Analysis("CMS_2018_I1662081") {}
 20
 21
 22    // Set up projections and book histograms
 23    void init() {
 24      // Complete final state
 25      FinalState fs(Cuts::abseta < 5);
 26
 27      // Dressed leptons
 28      ChargedLeptons charged_leptons(fs);
 29      IdentifiedFinalState photons(fs, PID::PHOTON);
 30
 31      PromptFinalState prompt_leptons(charged_leptons);
 32      prompt_leptons.acceptMuonDecays(true);
 33      prompt_leptons.acceptTauDecays(true);
 34      PromptFinalState prompt_photons(photons);
 35      prompt_photons.acceptMuonDecays(true);
 36      prompt_photons.acceptTauDecays(true);
 37      Cut looseLeptonCuts = Cuts::pt > 15*GeV && Cuts::abseta < 2.4;
 38
 39      LeptonFinder dressed_leptons(prompt_leptons, prompt_photons, 0.1, looseLeptonCuts);
 40      declare(dressed_leptons, "LeptonFinder");
 41
 42      // Projection for jets
 43      VetoedFinalState fsForJets(fs);
 44      fsForJets.addVetoOnThisFinalState(dressed_leptons);
 45      declare(FastJets(fsForJets, JetAlg::ANTIKT, 0.4), "Jets");
 46
 47      // Projections for MET
 48      declare(MissingMomentum(fs), "MET");
 49
 50      // Booking of histograms
 51      book(_hist_norm_met , 4, 1, 1);
 52      book(_hist_norm_ht  , 2, 1, 1);
 53      book(_hist_norm_st  , 3, 1, 1);
 54      book(_hist_norm_wpt , 5, 1, 1);
 55      book(_hist_norm_njets , 1, 1, 1);
 56      book(_hist_norm_lpt , 6, 1, 1);
 57      book(_hist_norm_labseta , 7, 1, 1);
 58
 59      book(_hist_abs_met , 11, 1, 1);
 60      book(_hist_abs_ht  , 9, 1, 1);
 61      book(_hist_abs_st  , 10, 1, 1);
 62      book(_hist_abs_wpt , 12, 1, 1);
 63      book(_hist_abs_njets , 8, 1, 1);
 64      book(_hist_abs_lpt , 13, 1, 1);
 65      book(_hist_abs_labseta , 14, 1, 1);
 66
 67    }
 68
 69
 70    // per event analysis
 71    void analyze(const Event& event) {
 72
 73      // Lepton veto selection
 74      const LeptonFinder& dressed_leptons = apply<LeptonFinder>(event, "LeptonFinder");
 75      if (dressed_leptons.dressedLeptons().size() != 1) vetoEvent;
 76
 77      // Signal lepton selection
 78      FourMomentum lepton = dressed_leptons.dressedLeptons()[0];
 79
 80      const double leptonPt = lepton.pT();
 81      const double leptonAbsEta = std::abs( lepton.eta() );
 82      if (leptonPt <= 26*GeV || leptonAbsEta >= 2.4) vetoEvent;
 83
 84      // Jet selection
 85      const FastJets& jetpro = apply<FastJets>(event, "Jets");
 86      const Jets jets = jetpro.jets(Cuts::abseta < 2.4 && Cuts::pT > 20*GeV);
 87      Jets cleanedJets;
 88      unsigned int nJetsAbove30GeV = 0;
 89      unsigned int nJetsAbove20GeV = 0;
 90      unsigned int nBJetsAbove30GeV = 0;
 91      unsigned int nBJetsAbove20GeV = 0;
 92      for (const Jet& j : jets) {
 93        cleanedJets.push_back( j );
 94        ++nJetsAbove20GeV;
 95        if ( j.pT() > 30*GeV) ++nJetsAbove30GeV;
 96
 97        if ( j.bTagged() ) {
 98          ++nBJetsAbove20GeV;
 99          if ( j.pT() > 30*GeV) ++nBJetsAbove30GeV;
100        }
101      }
102
103      if ( nJetsAbove30GeV < 3 || nJetsAbove20GeV < 4 ) vetoEvent;
104      if ( nBJetsAbove30GeV < 1 || nBJetsAbove20GeV < 2 ) vetoEvent;
105
106      // MET
107      const MissingMomentum& met = apply<MissingMomentum>(event, "MET");
108      _hist_norm_met->fill(met.visibleMomentum().pT()/GeV);
109      _hist_abs_met->fill(met.visibleMomentum().pT()/GeV);
110
111      // HT and ST
112      double ht = 0.0;
113      for (const Jet& j : cleanedJets) ht += j.pT();
114
115      double st = ht + lepton.pT() + met.visibleMomentum().pT();
116      _hist_norm_ht->fill(ht/GeV);
117      _hist_norm_st->fill(st/GeV);
118      _hist_abs_ht->fill(ht/GeV);
119      _hist_abs_st->fill(st/GeV);
120
121      // WPT
122      FourMomentum w = lepton - met.visibleMomentum();
123      _hist_norm_wpt->fill(w.pT()/GeV);
124      _hist_abs_wpt->fill(w.pT()/GeV);
125
126      // Lepton pt and eta
127      _hist_norm_lpt->fill( leptonPt/GeV);
128      _hist_norm_labseta->fill( leptonAbsEta/GeV);
129
130      _hist_abs_lpt->fill( leptonPt/GeV);
131      _hist_abs_labseta->fill( leptonAbsEta/GeV);
132
133      // NJets
134      _hist_norm_njets->fill( cleanedJets.size());
135      _hist_abs_njets->fill( cleanedJets.size());
136
137    }
138
139
140    void finalize() {
141      normalize(_hist_norm_met);
142      normalize(_hist_norm_ht);
143      normalize(_hist_norm_st);
144      normalize(_hist_norm_wpt);
145      normalize(_hist_norm_njets);
146      normalize(_hist_norm_lpt);
147      normalize(_hist_norm_labseta);
148
149      scale(_hist_abs_met, crossSection()/picobarn / sumOfWeights());
150      scale(_hist_abs_ht, crossSection()/picobarn / sumOfWeights());
151      scale(_hist_abs_st, crossSection()/picobarn / sumOfWeights());
152      scale(_hist_abs_wpt, crossSection()/picobarn / sumOfWeights());
153      scale(_hist_abs_njets, crossSection()/picobarn / sumOfWeights());
154      scale(_hist_abs_lpt, crossSection()/picobarn / sumOfWeights());
155      scale(_hist_abs_labseta, crossSection()/picobarn / sumOfWeights());
156
157    }
158
159
160  private:
161    Histo1DPtr _hist_norm_met, _hist_norm_ht, _hist_norm_st, _hist_norm_wpt, _hist_norm_njets, _hist_norm_lpt, _hist_norm_labseta;
162    Histo1DPtr _hist_abs_met, _hist_abs_ht, _hist_abs_st, _hist_abs_wpt, _hist_abs_njets, _hist_abs_lpt, _hist_abs_labseta;
163
164  };
165
166
167  RIVET_DECLARE_PLUGIN(CMS_2018_I1662081);
168
169}