Rivet analyses

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: - arXiv: 1607.00837

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

#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/PartonicTops.hh"
#include "Rivet/Projections/LeptonFinder.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
    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2016_I1473674);


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

      // Complete final state
      FinalState fs;

      // Parton level top quarks
      declare(PartonicTops(TopDecay::E_MU, PromptEMuFromTau::NO), "LeptonicPartonTops");
      declare(PartonicTops(TopDecay::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);
      declare(electrons, "Electrons");
      LeptonFinder dressed_electrons(electrons, photons, 0.1);
      declare(dressed_electrons, "DressedElectrons");
      //
      IdentifiedFinalState mu_id(fs);
      mu_id.acceptIdPair(PID::MUON);
      PromptFinalState muons(mu_id);
      declare(muons, "Muons");
      LeptonFinder dressed_muons(muons, photons, 0.1);
      declare(dressed_muons, "DressedMuons");

      // Projection for jets
      VetoedFinalState fs_jets;
      fs_jets.addVetoOnThisFinalState(dressed_muons);
      declare(FastJets(fs_jets, JetAlg::ANTIKT, 0.5), "Jets");

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


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


    /// Per-event analysis
    void analyze(const Event& event) {

      // 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 LeptonFinder& dressed_electrons = apply<LeptonFinder>(event, "DressedElectrons");
      const LeptonFinder& dressed_muons = apply<LeptonFinder>(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 = apply<MissingMomentum>(event, "MET");
      _hist_met->fill(met.visibleMomentum().pT()/GeV);

      // HT and ST
      const FastJets& jetpro = apply<FastJets>(event, "Jets");
      const Jets jets = jetpro.jetsByPt(Cuts::pT > 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);
      _hist_st->fill(st/GeV);

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


    /// 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;

  };


  RIVET_DECLARE_PLUGIN(CMS_2016_I1473674);

}