Rivet analyses

title: CMS_2016_I1454211

Boosted $t\bar{t}$ in $pp$ collisions at $\sqrt{s} = 8~\TeV$

Experiment: CMS (LHC)

Inspire ID: 1454211

Status: VALIDATED

Authors: - Salvatore Rappoccio - Maral Alyari - Julia Thom - Louise Skinnari - Susan Dittmer - Matthew Bellis

References: - Expt page: CMS-PAS-TOP-14-012 (PAS) - CERN-EP-2016-078 (paper)

Beams: p+ p+

Beam energies: (4000.0, 4000.0)GeV

Run details: - $pp$ QCD interactions at $\sqrt{s} = 8~\TeV with $t\bar{t}$ process. Data collected by CMS during the year 2012. Boosted topology restricts phase space, requiring high statistics in a single run or custom merging of the YODA files.

The cross section for pair production of top quarks with high transverse momenta ($p_\mathrm{T} > 400$~\GeV) is measured in 19.7~fb$^{-1}$ of $\mathrm{pp}$ collisions, collected with the CMS detector at $\sqrt{s} = 8~\TeV$. The measurement is performed for lepton+jets events, where one top quark decays according to $t \rightarrow Wb \rightarrow \ell \nu b$, with $\ell$ denoting an electron or muon, and the second top quark decays to an hadronic final state and is reconstructed as a single large-radius jet and identified as a top quark candidate using jet substructure techniques. Integrated cross sections, as well as differential cross sections as a function of the top quark $p_\mathrm{T}$ and rapidity, are measured both at particle level within a fiducial region resembling the detector-level selections and at parton level. RIVET: This analysis is to be run on $t\bar{t}$ Monte Carlo. It utilizes the PartonicTops projection, which assumes top quarks in the event record. The analysis has been validated with Powheg+Pythia6. The parton-level phase space is defined by requiring two PartonicTops. Exactly one PartonicTop must decay directly to a muon or electron (no intermediate tau), and exactly one PartonicTop decays hadronically. For $t\bar{t}$ Monte Carlo, this is equivalent to requiring the event to be semileptonic at parton level. The parton-level top quark is defined as the hadronically decaying top. The parton-level top quark is required to have $p_\mathrm{T} > 400~\GeV$. The particle-level phase space is defined using the following object definitions: - Lepton: A dressed electron or muon, meaning the lepton has been clustered with all photons within a cone of $R=0.1$. The DressedLepton projection is used to construct the dressed lepton. The lepton is required to have $p_\mathrm{T} > 45$~GeV and $|\eta| < 2.1$. - B Jet Candidate: Gen AK5 jets are formed by clustering the final state particles in the event using the anti-$k_{T}$ algorithm with distance parameter $R=0.5$. Neutrinos are excluded from the clustering, as are any particles included in the dressed lepton. The gen AK5 jet is required to have $p_{T} > 30$~GeV and $|\eta| < 2.4$. Gen AK5 jets in the same hemisphere as the lepton ($\Delta R(e/\mu,~\mathrm{jet}) < \pi/2$) are defined as $b$-jet candidates. - Top Jet Candidate: Gen CA8 jets are formed by clustering the final state particles in the event using the Cambridge-Aachen algorithm with distance parameter $R=0.8$. Neutrinos are excluded from the clustering, as are any particles included in the dressed lepton. The gen CA8 jet is required to have $p_{T} > 30$~GeV and $|\eta| < 2.4$. Gen CA8 jets which have $p_{T} > 400$~GeV, 140 GeV $<$ mass $<$ 250 GeV, and are in the opposite hemisphere from the lepton ($\Delta{R(e/\mu,\mathrm{jet})} > \pi/2$) are defined as top jet candidates. The particle-level phase space is defined by requiring $\geq 1$ b jet candidate, $\geq 1$ top jet candidate, and exactly one lepton. This is in addition to the parton-level semileptonic requirement. The highest-$p_\mathrm{T}$ top jet candidate is defined as the particle-level $t$ jet.

Source code:CMS_2016_I1454211.cc

```c++

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/InvMassFinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/MissingMomentum.hh"

include "Rivet/Projections/PartonicTops.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// Boosted ttbar in pp collisions at sqrtS = 8 TeV /// @todo Use persistent weight counters class CMS_2016_I1454211 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2016_I1454211);


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

  // Get options particle-level only.
  _mode = 0;
  if (getOption("TMODE") == "PARTICLE") _mode = 0;
  if (getOption("TMODE") == "BOTH") _mode = 1;

  // Complete final state
  FinalState fs;

  // Partonic tops
  // Need these for flavour determination, even if only plotting particle-level
  declare(PartonicTops(TopDecay::ELECTRON, PromptEMuFromTau::NO), "ElectronPartonTops");
  declare(PartonicTops(TopDecay::MUON, PromptEMuFromTau::NO), "MuonPartonTops");
  declare(PartonicTops(TopDecay::HADRONIC), "HadronicPartonTops");

  // Projection for electrons and muons
  IdentifiedFinalState photons(fs, PID::PHOTON);

  const Cut leptonCuts = Cuts::pt > 45 * GeV && Cuts::abseta < 2.1;

  IdentifiedFinalState el_id(fs, {{PID::ELECTRON, -PID::ELECTRON}});
  PromptFinalState electrons(el_id);
  LeptonFinder dressed_electrons(electrons, photons, 0.1, leptonCuts);
  declare(dressed_electrons, "DressedElectrons");

  IdentifiedFinalState mu_id(fs, {{PID::MUON, -PID::MUON}});
  PromptFinalState muons(mu_id);
  LeptonFinder dressed_muons(muons, photons, 0.1, leptonCuts);
  declare(dressed_muons, "DressedMuons");

  // Projection for jets
  VetoedFinalState fs_jets(fs);
  fs_jets.addVetoOnThisFinalState(dressed_muons);
  fs_jets.addVetoOnThisFinalState(dressed_electrons);
  fs_jets.vetoNeutrinos();
  declare(FastJets(fs_jets, JetAlg::ANTIKT, 0.5), "ak5jets");
  declare(FastJets(fs_jets, JetAlg::CAM, 0.8), "ca8jets");

  if (_mode == 1) {
    book(_hEl_topPt_parton, "d01-x01-y01");   // dsigma/dpt(top quark), el ch
    book(_hEl_topY_parton, "d03-x01-y01");    // dsigma/dy(top quark), el ch
    book(_hMu_topPt_parton, "d05-x01-y01");   // dsigma/dpt(top quark), mu ch
    book(_hMu_topY_parton, "d07-x01-y01");    // dsigma/dy(top quark), mu ch
    book(_hComb_topPt_parton, "d09-x01-y01"); // dsigma/dpt(top quark), comb ch
    book(_hComb_topY_parton, "d11-x01-y01");  // dsigma/dy(top quark), comb ch

    book(_hEl_topPt_parton_norm, "d13-x01-y01");   // 1/sigma dsigma/dpt(top quark), el ch
    book(_hEl_topY_parton_norm, "d15-x01-y01");    // 1/sigma dsigma/dy(top quark), el ch
    book(_hMu_topPt_parton_norm, "d17-x01-y01");   // 1/sigma dsigma/dpt(top quark), mu ch
    book(_hMu_topY_parton_norm, "d19-x01-y01");    // 1/sigma dsigma/dy(top quark), mu ch
    book(_hComb_topPt_parton_norm, "d21-x01-y01"); // 1/sigma dsigma/dpt(top quark), comb ch
    book(_hComb_topY_parton_norm, "d23-x01-y01");  // 1/sigma dsigma/dy(top quark), comb ch
  }

  book(_hEl_topPt_particle, "d02-x01-y01");        // dsigma/dpt(top jet), el ch
  book(_hEl_topY_particle, "d04-x01-y01");         // dsigma/dy(top jet), el ch
  book(_hMu_topPt_particle, "d06-x01-y01");        // dsigma/dpt(top jet), mu ch
  book(_hMu_topY_particle, "d08-x01-y01");         // dsigma/dy(top jet), mu ch
  book(_hComb_topPt_particle, "d10-x01-y01");      // dsigma/dpt(top jet), comb ch
  book(_hComb_topY_particle, "d12-x01-y01");       // dsigma/dy(top jet), comb ch
  book(_hEl_topY_particle_norm, "d16-x01-y01");    // 1/sigma dsigma/dy(top jet), el ch
  book(_hEl_topPt_particle_norm, "d14-x01-y01");   // 1/sigma dsigma/dpt(top jet), el ch
  book(_hComb_topY_particle_norm, "d24-x01-y01");  // 1/sigma dsigma/dy(top jet), comb ch
  book(_hMu_topPt_particle_norm, "d18-x01-y01");   // 1/sigma dsigma/dpt(top jet), mu ch
  book(_hMu_topY_particle_norm, "d20-x01-y01");    // 1/sigma dsigma/dy(top jet), mu ch
  book(_hComb_topPt_particle_norm, "d22-x01-y01"); // 1/sigma dsigma/dpt(top jet), comb ch

  book(_hMu_cutflow, "mu_cutflow", 7, -0.5, 6.5);
  book(_hEl_cutflow, "el_cutflow", 7, -0.5, 6.5);
}


// per event analysis
void analyze(const Event& event) {

  // Total-events cutflow entries
  _hMu_cutflow->fill(0.);
  _hEl_cutflow->fill(0.);

  // Do parton-level selection and channel determination
  // Note that channel determination relies on partonic info, even for the particle-level tops
  int partonCh = 0; //0 non-semi-lep, 1 muon, 2 electron
  const Particles muonpartontops = apply<ParticleFinder>(event, "MuonPartonTops").particlesByPt();
  const Particles electronpartontops = apply<ParticleFinder>(event, "ElectronPartonTops").particlesByPt();
  if (electronpartontops.size() == 0 && muonpartontops.size() == 1)
    partonCh = 1;
  else if (electronpartontops.size() == 1 && muonpartontops.size() == 0)
    partonCh = 2;
  else
    vetoEvent;
  const Particles hadronicpartontops = apply<ParticleFinder>(event, "HadronicPartonTops").particlesByPt();
  if (hadronicpartontops.size() != 1) vetoEvent;

  if (partonCh == 1) _hMu_cutflow->fill(1.); // muon at parton level
  if (partonCh == 2) _hEl_cutflow->fill(1.); // electron at parton level

  // Get hadronic parton-level top
  const FourMomentum& partonTopP4 = hadronicpartontops.front();

  // Do particle-level selection and channel determination
  const LeptonFinder& dressed_electrons = apply<LeptonFinder>(event, "DressedElectrons");
  const LeptonFinder& dressed_muons = apply<LeptonFinder>(event, "DressedMuons");

  bool passParticleLep = false, passParticleTop = false;
  FourMomentum lepton, particleTopP4;

  if (partonCh == 1 && dressed_muons.dressedLeptons().size() == 1
      && dressed_electrons.dressedLeptons().size() == 0) {
    passParticleLep = true;
    _hMu_cutflow->fill(3.); //muon at particle level
    lepton = dressed_muons.dressedLeptons()[0].momentum();
  }
  if (partonCh == 2 && dressed_muons.dressedLeptons().size() == 0
      && dressed_electrons.dressedLeptons().size() == 1) {
    passParticleLep = true;
    _hEl_cutflow->fill(3.); //electron at particle level
    lepton = dressed_electrons.dressedLeptons()[0].momentum();
  }

  if (passParticleLep) {

    // Jet cuts
    Cut jetCuts = Cuts::pt > 30 * GeV && Cuts::abseta < 2.4;
    Jets genBjets, genTjets;
    int nGenBjets = 0, nGenTjets = 0;

    const FastJets& AK5jets = apply<FastJets>(event, "ak5jets");
    for (const Jet& jet : AK5jets.jetsByPt(jetCuts)) {
      if (deltaR(jet, lepton) > M_PI / 2.0) continue;
      if (deltaR(jet, lepton) < 0.1) continue;
      genBjets.push_back(jet);
      nGenBjets += 1;
    }

    const FastJets& CA8jets = apply<FastJets>(event, "ca8jets");
    for (const Jet& jet : CA8jets.jetsByPt(jetCuts)) {
      if (deltaR(jet, lepton) < M_PI / 2.0) continue;
      if (jet.mass() < 140 * GeV) continue;
      if (jet.mass() > 250 * GeV) continue;
      genTjets.push_back(jet);
      nGenTjets += 1;
    }

    if (nGenBjets >= 1) {
      if (_mode == 1) {
        if (partonCh == 1) _hMu_cutflow->fill(4.); // muon at parton level
        if (partonCh == 2) _hEl_cutflow->fill(4.); // electron at parton level
      }
      if (nGenTjets >= 1) {
        passParticleTop = true;
        if (_mode == 1) {
          if (partonCh == 1) _hMu_cutflow->fill(5.); // muon at parton level
          if (partonCh == 2) _hEl_cutflow->fill(5.); // electron at parton level
        }
        particleTopP4 = genTjets[0];
      }
    }
  }

  if (partonCh == 1) {

    if (_mode == 1) {
      // protect against unphysical partons
      if (partonTopP4.E() < 0) {
        MSG_WARNING("Top parton with negative energy! Vetoing event. Try turning off partonic tops?");
        vetoEvent;
      }

      _hMu_topPt_parton->fill(partonTopP4.pT() / GeV);
      _hMu_topPt_parton_norm->fill(partonTopP4.pT() / GeV);
      _hComb_topPt_parton->fill(partonTopP4.pT() / GeV);
      _hComb_topPt_parton_norm->fill(partonTopP4.pT() / GeV);

      if (partonTopP4.pT() >= 400 * GeV) {
        _hMu_cutflow->fill(2.);
        _hMu_topY_parton->fill(partonTopP4.rapidity());
        _hMu_topY_parton_norm->fill(partonTopP4.rapidity());
        _hComb_topY_parton->fill(partonTopP4.rapidity());
        _hComb_topY_parton_norm->fill(partonTopP4.rapidity());
      }
    }

    if (passParticleTop) {
      _hMu_topPt_particle->fill(particleTopP4.pT() / GeV);
      _hMu_topPt_particle_norm->fill(particleTopP4.pT() / GeV);
      _hComb_topPt_particle->fill(particleTopP4.pT() / GeV);
      _hComb_topPt_particle_norm->fill(particleTopP4.pT() / GeV);

      if (particleTopP4.pT() >= 400 * GeV) {
        _hMu_cutflow->fill(6.);
        _hMu_topY_particle->fill(particleTopP4.rapidity());
        _hMu_topY_particle_norm->fill(particleTopP4.rapidity());
        _hComb_topY_particle->fill(particleTopP4.rapidity());
        _hComb_topY_particle_norm->fill(particleTopP4.rapidity());
      }
    }
  }

  if (partonCh == 2) {
    if (_mode == 1) {
      _hEl_topPt_parton->fill(partonTopP4.pT() / GeV);
      _hEl_topPt_parton_norm->fill(partonTopP4.pT() / GeV);
      _hComb_topPt_parton->fill(partonTopP4.pT() / GeV);
      _hComb_topPt_parton_norm->fill(partonTopP4.pT() / GeV);

      if (partonTopP4.pT() >= 400 * GeV) {
        _hEl_cutflow->fill(2.);
        _hEl_topY_parton->fill(partonTopP4.rapidity());
        _hEl_topY_parton_norm->fill(partonTopP4.rapidity());
        _hComb_topY_parton->fill(partonTopP4.rapidity());
        _hComb_topY_parton_norm->fill(partonTopP4.rapidity());
      }
    }

    if (passParticleTop) {
      _hEl_topPt_particle->fill(particleTopP4.pT() / GeV);
      _hEl_topPt_particle_norm->fill(particleTopP4.pT() / GeV);
      _hComb_topPt_particle->fill(particleTopP4.pT() / GeV);
      _hComb_topPt_particle_norm->fill(particleTopP4.pT() / GeV);

      if (particleTopP4.pT() >= 400 * GeV) {
        _hEl_cutflow->fill(6.);
        _hEl_topY_particle->fill(particleTopP4.rapidity());
        _hEl_topY_particle_norm->fill(particleTopP4.rapidity());
        _hComb_topY_particle->fill(particleTopP4.rapidity());
        _hComb_topY_particle_norm->fill(particleTopP4.rapidity());
      }
    }
  }
}

void finalize() {

  normalize(_hMu_topPt_particle_norm);
  normalize(_hMu_topY_particle_norm);
  normalize(_hEl_topPt_particle_norm);
  normalize(_hEl_topY_particle_norm);
  normalize(_hComb_topPt_particle_norm);
  normalize(_hComb_topY_particle_norm, 1.0, false);

  const double sf = crossSection() / femtobarn / sumOfWeights();
  scale(_hMu_topPt_particle, sf);
  scale(_hEl_topPt_particle, sf);
  scale(_hMu_topY_particle, sf);
  scale(_hEl_topY_particle, sf);
  scale(_hComb_topPt_particle, sf);
  scale(_hComb_topY_particle, sf);

  if (_mode == 1) {
    normalize(_hMu_topPt_parton_norm);
    normalize(_hMu_topY_parton_norm);
    normalize(_hEl_topPt_parton_norm);
    normalize(_hEl_topY_parton_norm);
    normalize(_hComb_topPt_parton_norm);
    normalize(_hComb_topY_parton_norm, 1.0, false);
    scale(_hMu_topPt_parton, sf);
    scale(_hEl_topPt_parton, sf);
    scale(_hMu_topY_parton, sf);
    scale(_hEl_topY_parton, sf);
    scale(_hComb_topPt_parton, sf);
    scale(_hComb_topY_parton, sf);
  }
}

protected:

size_t _mode;

private:

Histo1DPtr _hMu_topPt_parton, _hMu_topY_parton, _hEl_topPt_parton, _hEl_topY_parton, _hComb_topPt_parton,
    _hComb_topY_parton;
Histo1DPtr _hMu_topPt_particle, _hMu_topY_particle, _hEl_topPt_particle, _hEl_topY_particle,
    _hComb_topPt_particle, _hComb_topY_particle;
Histo1DPtr _hMu_topPt_parton_norm, _hMu_topY_parton_norm, _hEl_topPt_parton_norm, _hEl_topY_parton_norm,
    _hComb_topPt_parton_norm, _hComb_topY_parton_norm;
Histo1DPtr _hMu_topPt_particle_norm, _hMu_topY_particle_norm, _hEl_topPt_particle_norm,
    _hEl_topY_particle_norm, _hComb_topPt_particle_norm, _hComb_topY_particle_norm;
Histo1DPtr _hMu_cutflow, _hEl_cutflow;

};

RIVET_DECLARE_PLUGIN(CMS_2016_I1454211);

} ```