Rivet Analyses Reference

CMS_2018_I1663958

ttbar lepton+jets 13 TeV
Experiment: CMS (LHC)
Inspire ID: 1663958
Status: VALIDATED
Authors:
  • Otto Hindrichs
References:
  • arXiv: 1803.08856
  • CMS-TOP-17-002
  • Submitted to Phys. Rev. D.
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • pp QCD interactions at $\sqrt{s} = 13$ TeV. Data collected by CMS during the year 2015. Selection of lepton+jets top pair candidate events at particle level.

Abstract: Differential and double-differential cross sections for the production of top quark pairs in proton-proton collisions at $\sqrt{s} = 13$\,TeV are measured as a function of kinematic variables of the top quarks and the top quark-antiquark ($\text{t}\bar{\text{t}}$) system. In addition, kinematic variables and multiplicities of jets associated with the $\text{t}\bar{\text{t}}$ production are measured. This analysis is based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.8\,fb$^{-1}$. The measurements are performed in the lepton+jets decay channels with a single muon or electron and jets in the final state. The differential cross sections are presented at the particle level, within a phase space close to the experimental acceptance, and at the parton level in the full phase space. The results are compared to several standard model predictions that use different methods and approximations. The kinematic variables of the top quarks and the $\text{t}\bar{\text{t}}$ system are reasonably described in general, though none predict all the measured distributions. In particular, the transverse momentum distribution of the top quarks is more steeply falling than predicted. The kinematic distributions and multiplicities of jets are adequately modeled by certain combinations of next-to-leading-order calculations and parton shower models. Rivet: This analysis is to be run on $\text{t}\bar{\text{t}}$ Monte Carlo. The particle-level phase space is defined using the following definitions: \begin{description} \item[lepton]: an electron or muon with $p_\text{T}>30\,\text{GeV}$ and $|\eta|<2.4$, dressed within a cone of radius 0.1, \item[jet]: a jet is reconstructed with the anti-$k_\text{T}$ algorithm with a radius of 0.4, after removing the neutrinos and dressed leptons, with $p_\text{T]>25\,\text{GeV}$ and $|\eta|<2.4$, \item[b-jet]: a jet that contains a B-hadron. \end{description} A W boson is reconstructed from a lepton and the sum of the neutrino energies, while another W boson is reconstructed from a light jet pair. The two top quarks are reconstructed by combining b jets to these W boson. A check based on the W boson and top quark masses is performed to choose the proper combinations.

Source code: CMS_2018_I1663958.cc
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#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/DressedLeptons.hh"
#include "Rivet/Tools/BinnedHistogram.hh"

namespace Rivet {


  /// @brief ttbar lepton+jets 13 TeV
  class CMS_2018_I1663958 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2018_I1663958);

    void init() {

      const FinalState fs(Cuts::abseta < 6.);
      const VisibleFinalState vfs(Cuts::abseta < 6.);

      VetoedFinalState invisibles(fs);
      invisibles.addVetoOnThisFinalState(vfs);
      declare(invisibles, "Invisibles");

      FinalState all_photons(vfs, Cuts::abspid == PID::PHOTON);
      FinalState leptons(vfs, Cuts::abspid == PID::ELECTRON || Cuts::abspid == PID::MUON);

      DressedLeptons dressed_leptons(all_photons, leptons, 0.1, Cuts::abseta < 2.4 && Cuts::pT > 15*GeV, true);
      declare(dressed_leptons, "MyLeptons");

      VetoedFinalState photons(all_photons);
      photons.addVetoOnThisFinalState(dressed_leptons);
      declare(photons, "MyPhotons");

      VetoedFinalState isolationparticles(vfs);
      isolationparticles.addVetoOnThisFinalState(dressed_leptons);
      declare(isolationparticles, "IsoParticles");

      declare(FastJets(vfs, FastJets::ANTIKT, 0.4), "Jets");

      book(_h["thadpt"], 1, 1, 1);
      book(_h["thady"],  3, 1, 1);
      book(_h["tleppt"], 5, 1, 1);
      book(_h["tlepy"],  7, 1, 1);
      book(_h["ttm"],    9, 1, 1);
      book(_h["ttpt"],  11, 1, 1);
      book(_h["tty"],   13, 1, 1);
      book(_h["njet"],  15, 1, 1);
      /// @todo Memory leak
      vector<double> njetbins = {-0.5, 0.5, 1.5, 2.5, 3.5};
      for (size_t i = 0; i < njetbins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["njet_ttm"].add(njetbins[i], njetbins[i+1], book(tmp, 17 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["njet_ttm_norm"].add(njetbins[i], njetbins[i+1], book(tmp, 99 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["njet_thadpt"].add(njetbins[i], njetbins[i+1], book(tmp, 22 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["njet_thadpt_norm"].add(njetbins[i], njetbins[i+1], book(tmp, 104 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["njet_ttpt"].add(njetbins[i], njetbins[i+1], book(tmp, 27 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["njet_ttpt_norm"].add(njetbins[i], njetbins[i+1], book(tmp, 109 + i, 1, 1)); }
      }
      vector<double> thadybins = {0.0, 0.5, 1.0, 1.5, 2.5};
      for (size_t i = 0; i < thadybins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["thady_thadpt"].add(thadybins[i], thadybins[i+1], book(tmp, 32 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["thady_thadpt_norm"].add(thadybins[i], thadybins[i+1], book(tmp, 114 + i, 1, 1)); }
      }
      vector<double> ttmbins = {300., 450., 625., 850., 2000.};
      for (size_t i = 0; i < ttmbins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["ttm_tty"].add(ttmbins[i], ttmbins[i+1], book(tmp, 37 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["ttm_tty_norm"].add(ttmbins[i], ttmbins[i+1], book(tmp, 119 + i, 1, 1)); }
      }
      vector<double> thadptbins = {0., 90., 180., 270., 800.};
      for (size_t i = 0; i < thadptbins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["thadpt_ttm"].add(thadptbins[i], thadptbins[i+1], book(tmp, 42 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["thadpt_ttm_norm"].add(thadptbins[i], thadptbins[i+1], book(tmp, 124 + i, 1, 1)); }
      }
      vector<double> jetbins = {-0.5, 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5};
      for (size_t i = 0; i < jetbins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["jetspt"].add(jetbins[i], jetbins[i+1], book(tmp, 47 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetspt_norm"].add(jetbins[i], jetbins[i+1], book(tmp, 129 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetseta"].add(jetbins[i], jetbins[i+1], book(tmp, 56 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetseta_norm"].add(jetbins[i], jetbins[i+1], book(tmp, 138 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetsdr"].add(jetbins[i], jetbins[i+1], book(tmp, 65 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetsdr_norm"].add(jetbins[i], jetbins[i+1], book(tmp, 147 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetsdrtops"].add(jetbins[i], jetbins[i+1], book(tmp, 74 + i, 1, 1)); }
        { Histo1DPtr tmp; _b["jetsdrtops_norm"].add(jetbins[i], jetbins[i+1], book(tmp, 156 + i, 1, 1)); }
      }
      vector<double> njetsptbins = {0., 40., 60., 80., 120.};
      for (size_t i = 0; i < njetsptbins.size() - 1; ++i) {
        { Histo1DPtr tmp; _b["njetspt"].add(njetsptbins[i], njetsptbins[i+1], book(tmp, 169 + i, 1, 1)); }
      }

      book(_h["thadpt_norm"], 83, 1, 1);
      book(_h["thady_norm"],  85, 1, 1);
      book(_h["tleppt_norm"], 87, 1, 1);
      book(_h["tlepy_norm"],  89, 1, 1);
      book(_h["ttm_norm"],    91, 1, 1);
      book(_h["ttpt_norm"],   93, 1, 1);
      book(_h["tty_norm"],    95, 1, 1);
      book(_h["njet_norm"],   97, 1, 1);
      /// @todo Memory leak?
      book(m_hist_gap1, "d165-x01-y01");
      book(m_hist_gap2, "d167-x01-y01");
    }


    void analyze(const Event& event) {

      Jets bjets, ljets;
      Particles leptons, vetoleptons, additionalobjects, additionaljets;

      const Particles& isopars = apply<VetoedFinalState>(event, "IsoParticles").particles();
      const Particles& dressedleptons = apply<DressedLeptons>(event, "MyLeptons").particles();
      for (const Particle& lep : dressedleptons) {
        double isolation = sum(filter_select(isopars, deltaRLess(lep, 0.4)), Kin::pT, 0.);
        isolation = isolation/lep.pt();
        if (isolation > 0.35) continue;
        if (lep.pt() > 30*GeV && lep.abseta() < 2.4) leptons += lep;
        else if(lep.pt() > 15*GeV && lep.abseta() < 2.4)  vetoleptons += lep;
      }

      const Particles& photons = apply<VetoedFinalState>(event, "MyPhotons").particles(Cuts::abseta < 2.4 && Cuts::pT > 15*GeV);
      for (const Particle& ph : photons) {
        double isolation = sum(filter_select(isopars, deltaRLess(ph, 0.4)), Kin::pT, 0.);
        isolation = isolation/ph.pt() - 1.;
        if (isolation > 0.25) continue;
        additionalobjects += ph;
      }

      FourMomentum invsum(0.,0.,0.,0.);
      const Particles& invfspars = apply<FinalState>(event, "Invisibles").particles();
      for (const Particle& par : invfspars) invsum += par.mom();

      Jets allJets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::abseta < 2.4 && Cuts::pT > 25*GeV);
      idiscardIfAnyDeltaRLess(allJets, leptons, 0.4);
      idiscardIfAnyDeltaRLess(allJets, vetoleptons, 0.4);
      idiscardIfAnyDeltaRLess(allJets, additionalobjects, 0.4);
      for (const Jet& jet : allJets) {
        if (jet.bTagged())  bjets += jet;
        else                ljets += jet;
      }

      //Semi-leptonic reconstruction
      if (leptons.size() != 1 || vetoleptons.size() || bjets.size() < 2 || ljets.size() < 2)  vetoEvent;

      FourMomentum wl = invsum + leptons[0].mom();

      Particle thad, tlep;
      Particles tlep_decay(3), thad_decay(3);
      double Kmin = numeric_limits<double>::max();
      for (size_t a = 0 ; a <  ljets.size() ; ++a){
        const Jet& lja = ljets[a];
        for (size_t b = 0 ; b < a ; ++b) {
          const Jet& ljb = ljets[b];
          FourMomentum wh(lja.momentum() + ljb.momentum());
          for (const Jet& bjh : bjets) {
            FourMomentum th(wh + bjh.momentum());
            for (const Jet& bjl : bjets) {
              if (&bjh == &bjl) continue;
              FourMomentum tl(wl + bjl.momentum());

              double K = pow(wh.mass() - 80.4, 2) + pow(th.mass() - 172.5, 2) + pow(tl.mass() - 172.5, 2);
              if (K < Kmin)
              {
                Kmin = K;
                thad = Particle(6, th);
                thad_decay[0] = Particle(5, bjh);
                thad_decay[1] = lja.pt() > ljb.pt() ? Particle(1, lja) : Particle(1, ljb);
                thad_decay[2] = lja.pt() <= ljb.pt() ? Particle(1, lja) : Particle(1, ljb);
                tlep = Particle(-6, tl);
                tlep_decay[0] = Particle(5, bjl);
                tlep_decay[1] = leptons[0];
                tlep_decay[2] = Particle(-1*(leptons[0].pid()+1), invsum);
              }
            }
          }
        }
      }

      Particles tt_jets({ tlep_decay[0], thad_decay[0], thad_decay[1], thad_decay[2] });

      const double eps = 1E-5;
      for (const Jet& jet : bjets) {
        if(jet.pt() < 30*GeV || jet.abseta() > 2.4) continue;
        if(find_if(tt_jets.begin(), tt_jets.end(), [&](const Particle& par){return deltaR(jet, par) < eps;}) != tt_jets.end()) continue;
        additionaljets += Particle(5, jet.mom());
      }
      for (const Jet& jet : ljets) {
        if(jet.pt() < 30*GeV || jet.abseta() > 2.4) continue;
        if(find_if(tt_jets.begin(), tt_jets.end(), [&](const Particle& par){return deltaR(jet, par) < eps;}) != tt_jets.end()) continue;
        if(jet.cTagged())  additionaljets += Particle(4, jet.mom());
        else               additionaljets += Particle(1, jet.mom());
      }

      sort(additionaljets.begin(), additionaljets.end(), cmpMomByPt);

      FourMomentum tt(thad.mom() + tlep.mom());

      dualfill("thadpt", thad.pt()/GeV);
      dualfill("thady", thad.absrap());
      dualfill("tleppt", tlep.pt()/GeV);
      dualfill("tlepy", tlep.absrap());
      dualfill("ttm", tt.mass()/GeV);
      dualfill("ttpt", tt.pt()/GeV);
      dualfill("tty", tt.absrap());
      dualfill("njet", min(additionaljets.size(), (size_t)5));
      double njet = double(min((size_t)3, additionaljets.size()));
      dualfill("njet_ttm", njet, tt.mass()/GeV);
      dualfill("njet_thadpt", njet, thad.pt()/GeV);
      dualfill("njet_ttpt", njet, tt.pt()/GeV);
      dualfill("thady_thadpt", thad.absrap(), thad.pt()/GeV);
      dualfill("ttm_tty", tt.mass()/GeV, tt.absrap());
      dualfill("thadpt_ttm", thad.pt()/GeV, tt.mass()/GeV);
      int jpos = -1;
      for (const Particles& jets : {tt_jets, additionaljets}) {
        for (const Particle& jet : jets) {
          jpos++;
          dualfill("jetspt", jpos, jet.pt()/GeV);
          dualfill("jetseta", jpos, jet.abseta());
          double drmin = 1E10;
          for (const Particle& tjet : tt_jets) {
            double dr = deltaR(jet, tjet);
            if(dr > eps && dr < drmin)  drmin = dr;
          }
          dualfill("jetsdr", jpos, drmin);
          dualfill("jetsdrtops", jpos, min(deltaR(jet, thad), deltaR(jet, tlep)));
        }
      }
      for (double ptcut : {30, 50, 75, 100}) {
        _b["njetspt"].fill(ptcut , count_if(additionaljets.begin(), additionaljets.end(),
                                            [&ptcut](const Particle& j) {return j.pt() > ptcut;}));
      }
    }

    void dualfill(const string& tag, const double value) {
      _h[tag]->fill(value);  _h[tag + "_norm"]->fill(value);
    }

    void dualfill(const string& tag, const double val1, const double val2) {
      _b[tag].fill(val1, val2);  _b[tag + "_norm"].fill(val1, val2);
    }

    void gapfractionfromjetpt(const string& tag, Scatter2DPtr hgap, size_t njet) {
      size_t hn = njet+3;
      const double total = _b[tag].histo(0)->integral();
      const double totalj = _b[tag].histo(hn)->integral();
      double acc = total-totalj;
      double gf = acc/total;
      if (!std::isnan(gf)) {
        for (size_t nb = 0 ; nb < _b[tag].histo(hn)->numBins() ; ++nb) {
          const double bl = _b[tag].histo(njet+3)->bin(nb).xMin();
          const double bh = _b[tag].histo(njet+3)->bin(nb).xMax();
          const double bc = 0.5*(bh+bl);
          hgap->addPoint(bc, gf, bc-bl, bh-bc, 0., 0.);
          acc += _b[tag].histo(njet+3)->bin(nb).area();
          gf = acc/total;
        }
      } else  MSG_WARNING("Gap fraction is NaN. Histogram not produced.");
    }


    void finalize() {

      const double sf = crossSection()/sumOfWeights();

      gapfractionfromjetpt("jetspt", m_hist_gap1, 1);
      gapfractionfromjetpt("jetspt", m_hist_gap2, 2);

      for (auto& item : _h) {
        if (item.first.find("_norm") != string::npos) {
          normalize(item.second, 1.0, false);
        }
        else  scale(item.second, sf);
      }

      for (auto& item : _b) {
        if (item.first.find("_norm") != string::npos) {
          double area = 0;
          for (auto& hist : item.second.histos()) {  area += hist->sumW(false); }
          //normalize(item.second.histos(), 1.0, false);
          if (area)  item.second.scale(1/area, this);
        }
        else if (item.first.find("njetspt") != string::npos) {
          // skip division by bin width for secondary axis
          for (auto& hist : item.second.histos()) { scale(hist, sf); }
        }
        else  item.second.scale(sf, this);
      }

    }

    map<string,Histo1DPtr> _h;
    map<string,BinnedHistogram> _b;

    Scatter2DPtr m_hist_gap1;
    Scatter2DPtr m_hist_gap2;

  };


  RIVET_DECLARE_PLUGIN(CMS_2018_I1663958);
}

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