Rivet analyses

title: CMS_2022_I2129461

tW single top-quark differential cross sections at 13 TeV

Experiment: CMS (LHC)

Inspire ID: 2129461

Status: VALIDATED

Authors: - Victor Rodriguez Bouza

References: - arXiv: 2208.00924 - Expt page: CMS-TOP-21-010 - Accepted by JHEP

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at $\sqrt{s}=$ 13 TeV

Measurements of the inclusive and normalised differential cross sections are presented for the production of single top quarks in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data used were recorded with the CMS detector at the LHC during 2016-2018, and correspond to an integrated luminosity of $138 fb^{-1}$. Events containing one electron and one muon in the final state are analysed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events is used to separate the signal from the dominant $t\bar{t}$ background. A cross section of $79.2 \pm 0.9 (stat) ^{7.7}_{-8.0} (syst) \pm 1.2 (lumi) pb$ is obtained, consistent with the predictions of the standard model. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requirement of exactly one jet coming from the fragmentation of a bottom quark. The resulting distributions are unfolded to particle level and agree with the predictions at next-to-leading order in perturbative quantum chromodynamics.

Source code:CMS_2022_I2129461.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedLeptons.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/MissingMomentum.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// @brief Normalised differential cross sections for 13 TeV tW-channel single top-quark production class CMS_2022_I2129461 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2022_I2129461);


/// Book histograms and initialise projections before the run
void init() {

  // final state of all stable particles
  Cut particle_cut = (Cuts::abseta < 5.0) and (Cuts::pT > 0. * MeV);
  FinalState fs(particle_cut);

  // select charged leptons
  ChargedLeptons charged_leptons(fs);

  // select final state photons for dressed lepton clustering
  IdentifiedFinalState photons(fs);
  photons.acceptIdPair(PID::PHOTON);

  // select final state prompt charged leptons
  PromptFinalState prompt_leptons(charged_leptons);
  prompt_leptons.acceptMuonDecays(true);
  prompt_leptons.acceptTauDecays(true);

  // select final state prompt photons
  PromptFinalState prompt_photons(photons);
  prompt_photons.acceptMuonDecays(true);
  prompt_photons.acceptTauDecays(true);

  // Dressed leptons from selected prompt charged leptons and photons
  Cut lepton_cut = ((Cuts::abseta < 2.4) && (Cuts::pT > 20. * GeV)
                    && (((Cuts::abspid == PID::ELECTRON)
                         && ((Cuts::abseta < 1.4442) or (Cuts::abseta > 1.566)))
                        || (Cuts::abspid == PID::MUON)));

  LeptonFinder dressed_leptons(prompt_photons, prompt_leptons, 0.1, lepton_cut);
  declare(dressed_leptons, "LeptonFinder");

  // Jets
  VetoedFinalState fsForJets(fs);
  fsForJets.addVetoOnThisFinalState(dressed_leptons);
  declare(
      // excludes all neutrinos by default
      FastJets(fsForJets, JetAlg::ANTIKT, 0.4), "Jets");

  // pTmiss
  declare(MissingMomentum(fs), "MET");

  // book histograms
  book(_hist_norm_lep1_pt, "d06-x01-y08");
  book(_hist_norm_lep1lep2jet1_pz, "d07-x01-y08");
  book(_hist_norm_jet1_pt, "d08-x01-y08");
  book(_hist_norm_lep1lep2jet1_m, "d09-x01-y08");
  book(_hist_norm_lep1lep2_dphi, "d10-x01-y08");
  book(_hist_norm_lep1lep2jet1met_mt, "d11-x01-y08");
}


/// @brief Perform the per-event analysis
void analyze(const Event& event) {
  DressedLeptons dressedLeptons = apply<LeptonFinder>(event, "LeptonFinder").dressedLeptons();

  // Require at least two dressed leptons
  if (dressedLeptons.size() < 2) vetoEvent;

  // Require that the leading ones are an electron and a muon of opposite charge
  if (abs(dressedLeptons.at(0).pid() + dressedLeptons.at(1).pid()) != 2) vetoEvent;

  // Require that the leading lepton has at least 25 GeV of pT
  if (dressedLeptons.at(0).pt() <= 25. * GeV) vetoEvent;

  // Require that all identified lepton pairs have at least 20 GeV of invariant mass
  for (int iL = 0; iL < int(dressedLeptons.size()); iL++) {
    for (int jL = iL + 1; jL < int(dressedLeptons.size()); jL++) {
      if ((dressedLeptons.at(iL).momentum() + dressedLeptons.at(jL).momentum()).mass() <= 20. * GeV)
        vetoEvent;
    }
  }

  // Jet object ID
  Cut jet_cut((Cuts::abseta < 2.4) and (Cuts::pT > 20. * GeV));
  vector<Jet> jets = apply<FastJets>(event, "Jets").jets(jet_cut);

  // ignore jets that overlap with dressed leptons within dR < 0.4 and collect them in loose jets and jets categories
  Jets cleanedLooseJets;
  Jets cleanedJets;
  idiscardIfAnyDeltaRLess(jets, dressedLeptons, 0.4);
  for (const Jet& jet : jets) {
    if (jet.pt() > 30. * GeV)
      cleanedJets.push_back(jet);
    else
      cleanedLooseJets.push_back(jet);
  }

  if (cleanedJets.size() != 1) vetoEvent;         // select events with exactly one jet...
  if (not cleanedJets.at(0).bTagged()) vetoEvent; // ...that must be b-tagged...
  if (cleanedLooseJets.size() > 0) vetoEvent;     // ...and no loose jets

  // fill the histograms
  _hist_norm_lep1_pt->fill(min(max(dressedLeptons.at(0).pt(), 26. * GeV), 149. * GeV) / GeV);
  FourMomentum llj = dressedLeptons.at(0).momentum() + dressedLeptons.at(1).momentum()
      + cleanedJets.at(0).momentum();
  _hist_norm_lep1lep2jet1_pz->fill(min(max(abs((llj).pz()), 1. * GeV), 449. * GeV) / GeV);
  _hist_norm_jet1_pt->fill(min(max(cleanedJets.at(0).pt(), 31. * GeV), 149. * GeV) / GeV);
  _hist_norm_lep1lep2jet1_m->fill(min(max((llj).mass(), 51. * GeV), 399. * GeV) / GeV);
  _hist_norm_lep1lep2_dphi->fill(abs(deltaPhi(dressedLeptons.at(0).phi(), dressedLeptons.at(1).phi()))
                                 / PI);

  Vector3 tmpPtmiss3 = apply<MissingMomentum>(event, "MET").vectorPt();
  tmpPtmiss3.setZ(0.);
  FourMomentum ptmiss = FourMomentum(tmpPtmiss3.mod(), -tmpPtmiss3.x(), -tmpPtmiss3.y(), 0.);
  FourMomentum tmpM = llj + ptmiss;
  _hist_norm_lep1lep2jet1met_mt->fill(min(max(sqrt(tmpM.E2() - tmpM.pz2()), 101. * GeV), 499. * GeV)
                                      / GeV);
}

/// @brief Normalise histograms after the run
void finalize() {
  normalize(_hist_norm_lep1_pt);
  normalize(_hist_norm_lep1lep2jet1_pz);
  normalize(_hist_norm_jet1_pt);
  normalize(_hist_norm_lep1lep2jet1_m);
  normalize(_hist_norm_lep1lep2_dphi);
  normalize(_hist_norm_lep1lep2jet1met_mt);
}

private:

// Declaration of histograms
Histo1DPtr _hist_norm_lep1_pt;
Histo1DPtr _hist_norm_lep1lep2jet1_pz;
Histo1DPtr _hist_norm_jet1_pt;
Histo1DPtr _hist_norm_lep1lep2jet1_m;
Histo1DPtr _hist_norm_lep1lep2_dphi;
Histo1DPtr _hist_norm_lep1lep2jet1met_mt;

};

RIVET_DECLARE_PLUGIN(CMS_2022_I2129461); } ```