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CMS_2016_I1473674

Measurement of the differential cross sections for top quark pair production as a function of kinematic event variables at sqrt(s) = 8 TeV
Experiment: CMS (LHC)
Inspire ID: 1473674
Status: VALIDATED
Authors:
  • Markus Seidel
  • Lukas Kreczko
  • Emyr Clement
References: Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • ttbar events at sqrt(s) = 8 TeV (inclusive or lepton+jets decay mode) Top quarks are expected in the event record to identify the decay mode.

Measurements are reported of the normalized differential cross sections for top quark pair production with respect to four kinematic event variables: the missing transverse energy; the scalar sum of the jet transverse momentum (pT); the scalar sum of the pT of all objects in the event; and the pT of leptonically decaying W bosons from top quark decays.

Source code: CMS_2016_I1473674.cc
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#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/PartonicTops.hh"
#include "Rivet/Projections/DressedLeptons.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/InvMassFinalState.hh"
#include "Rivet/Projections/MissingMomentum.hh"

namespace Rivet {


  class CMS_2016_I1473674 : public Analysis {
  public:

    // Minimal constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(CMS_2016_I1473674);


    // Set up projections and book histograms
    void init() {

      // Complete final state
      FinalState fs;

      // Parton level top quarks
      declare(PartonicTops(PartonicTops::E_MU, false), "LeptonicPartonTops");
      declare(PartonicTops(PartonicTops::HADRONIC),    "HadronicPartonTops");

      // Projections for dressed electrons and muons
      IdentifiedFinalState photons(fs);
      photons.acceptIdPair(PID::PHOTON);
      //
      IdentifiedFinalState el_id(fs);
      el_id.acceptIdPair(PID::ELECTRON);
      PromptFinalState electrons(el_id);
      addProjection(electrons, "Electrons");
      DressedLeptons dressed_electrons(photons, electrons, 0.1);
      addProjection(dressed_electrons, "DressedElectrons");
      //
      IdentifiedFinalState mu_id(fs);
      mu_id.acceptIdPair(PID::MUON);
      PromptFinalState muons(mu_id);
      addProjection(muons, "Muons");
      DressedLeptons dressed_muons(photons, muons, 0.1);
      addProjection(dressed_muons, "DressedMuons");

      // Projection for jets
      VetoedFinalState fs_jets(FinalState(-MAXDOUBLE, MAXDOUBLE, 0*GeV));
      fs_jets.addVetoOnThisFinalState(dressed_muons);
      addProjection(FastJets(fs_jets, FastJets::ANTIKT, 0.5), "Jets");

      // Projections for MET
      addProjection(MissingMomentum(), "MET");


      // Booking of histograms
      _hist_met = bookHisto1D(5, 1, 1);
      _hist_ht  = bookHisto1D(6, 1, 1);
      _hist_st  = bookHisto1D(7, 1, 1);
      _hist_wpt = bookHisto1D(8, 1, 1);
    }


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

      // Select ttbar -> lepton+jets at parton level, removing tau decays
      const Particles leptonicpartontops = apply<ParticleFinder>(event, "LeptonicPartonTops").particlesByPt();
      if (leptonicpartontops.size() != 1) vetoEvent;
      const Particles hadronicpartontops = apply<ParticleFinder>(event, "HadronicPartonTops").particlesByPt();
      if (hadronicpartontops.size() != 1) vetoEvent;

      // Select ttbar -> lepton+jets at particle level
      const DressedLeptons& dressed_electrons = applyProjection<DressedLeptons>(event, "DressedElectrons");
      const DressedLeptons& dressed_muons = applyProjection<DressedLeptons>(event, "DressedMuons");
      if (dressed_electrons.dressedLeptons().size() + dressed_muons.dressedLeptons().size() != 1) vetoEvent;
      const FourMomentum lepton = (dressed_electrons.dressedLeptons().empty() ? dressed_muons : dressed_electrons).dressedLeptons()[0];

      // MET
      const MissingMomentum& met = applyProjection<MissingMomentum>(event, "MET");
      _hist_met->fill(met.visibleMomentum().pT()/GeV, weight);

      // HT and ST
      const FastJets& jetpro = applyProjection<FastJets>(event, "Jets");
      const Jets jets = jetpro.jetsByPt(20*GeV);

      double ht = 0.0;
      for (const Jet& j : jets) {
        if (deltaR(j.momentum(), lepton) > 0.3) {
          ht += j.pT();
        }
      }

      double st = ht + lepton.pT() + met.visibleMomentum().pT();
      _hist_ht->fill(ht/GeV, weight);
      _hist_st->fill(st/GeV, weight);

      // WPT
      const FourMomentum w = lepton - met.visibleMomentum();
      _hist_wpt->fill(w.pT()/GeV, weight);
    }


    /// Normalize histograms
    void finalize() {
      normalize(_hist_met);
      normalize(_hist_ht);
      normalize(_hist_st);
      normalize(_hist_wpt);
    }

  private:
    Histo1DPtr _hist_met, _hist_ht, _hist_st, _hist_wpt;

  };


  DECLARE_RIVET_PLUGIN(CMS_2016_I1473674);

}