Rivet analyses

title: ATLAS_2015_I1397635

$Wt$ at 8 TeV

Experiment: ATLAS (LHC)

Inspire ID: 1397635

Status: VALIDATED

Authors: - Reinhard Schwienhorst

References: - Expt page: ATLAS-TOPQ-2012-20 - JHEP01 (2016) 064 - DOI: 10.1007/JHEP01(2016)064 - arXiv: 1510.03752

Beams: p+ p+

Beam energies: (4000.0, 4000.0)GeV

Run details: - Single top $Wt$ + top--antitop production

Fiducial cross-section for $Wt+t\bar{t}$ production in events with two leptons and exactly one jet, using an integrated luminosity of 20.3 fb${}^{-1}$ of proton-proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section for the production of a top quark and a $W$ boson is measured in a fiducial acceptance requiring two leptons with $\pT > 25$ GeV and $|\eta| < 2.5$, one jet with $\pT > 20$ GeV and $|\eta| < 2.5$, and $E^\text{miss}_\text{T} > 20$ GeV, including both $Wt$ and top-quark pair events as signal. The measured value of the fiducial cross-section is $0.85 \pm 0.01$ (stat.) $\pm 0.07$ (syst.) $\pm 0.03$ (lumi.) pb.

Source code:ATLAS_2015_I1397635.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// $Wt$ at 8 TeV class ATLAS_2015_I1397635 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2015_I1397635);


void init() {

  // Eta ranges
  Cut eta_full = Cuts::abseta < 5.0 && Cuts::pT >= 1.0 * MeV;
  Cut eta_lep = Cuts::abseta < 2.5;

  // All final state particles
  FinalState fs(eta_full);

  // Get photons to dress leptons
  IdentifiedFinalState photons(fs);
  photons.acceptIdPair(PID::PHOTON);

  // Projection to find the electrons
  IdentifiedFinalState el_id(fs);
  el_id.acceptIdPair(PID::ELECTRON);
  PromptFinalState electrons(el_id);
  electrons.acceptTauDecays(true);
  declare(electrons, "electrons");
  LeptonFinder dressedelectrons(electrons, photons, 0.1, eta_lep && Cuts::pT > 25 * GeV);
  declare(dressedelectrons, "dressedelectrons");
  LeptonFinder ewdressedelectrons(electrons, photons, 0.1, eta_full);

  // Projection to find the muons
  IdentifiedFinalState mu_id(fs);
  mu_id.acceptIdPair(PID::MUON);
  PromptFinalState muons(mu_id);
  muons.acceptTauDecays(true);
  declare(muons, "muons");
  LeptonFinder dressedmuons(muons, photons, 0.1, eta_lep && Cuts::pT > 25 * GeV);
  declare(dressedmuons, "dressedmuons");
  LeptonFinder ewdressedmuons(muons, photons, 0.1, eta_full);

  // Projection to find neutrinos and produce MET
  IdentifiedFinalState nu_id;
  nu_id.acceptNeutrinos();
  PromptFinalState neutrinos(nu_id);
  neutrinos.acceptTauDecays(true);
  declare(neutrinos, "neutrinos");

  // Jet clustering.
  VetoedFinalState vfs;
  vfs.addVetoOnThisFinalState(ewdressedelectrons);
  vfs.addVetoOnThisFinalState(ewdressedmuons);
  vfs.addVetoOnThisFinalState(neutrinos);
  FastJets jets(vfs, JetAlg::ANTIKT, 0.4);
  jets.useInvisibles();
  declare(jets, "jets");

  book(_histo, 1, 1, 1);
}


void analyze(const Event& event) {

  // Get the selected objects, using the projections.
  DressedLeptons electrons = apply<LeptonFinder>(event, "dressedelectrons").dressedLeptons();
  DressedLeptons muons = apply<LeptonFinder>(event, "dressedmuons").dressedLeptons();
  // also make basic event selection cuts for leptons
  if (electrons.empty() && muons.empty()) vetoEvent;
  if (electrons.size() + muons.size() != 2) vetoEvent;

  // next selection cuts for jets
  const Jets jets = apply<FastJets>(event, "jets")
                        .jets(Cuts::pT > 20 * GeV && Cuts::abseta < 2.5, cmpMomByPt);
  if (jets.size() != 1) vetoEvent;

  // and selection cuts for b-tagging
  Jets bjets;
  // Check overlap of jets/leptons.
  for (Jet jet : jets) {
    // if dR(el,jet) < 0.4 skip the event
    for (DressedLepton el : electrons) {
      if (deltaR(jet, el) < 0.4) vetoEvent;
    }
    // if dR(mu,jet) < 0.4 skip the event
    for (DressedLepton mu : muons) {
      if (deltaR(jet, mu) < 0.4) vetoEvent;
    }
    // Count the number of b-tags
    // We have to check that the ghost-matched B hadrons have pT > 5 GeV
    // By default jet.bTags() returns all B hadrons without cuts
    bool btagged = jet.bTags(Cuts::pT >= 5 * GeV).size();
    if (btagged) bjets += jet;
  }
  if (bjets.size() != 1) vetoEvent;

  // Now evaluate MET selection
  // Get the neutrinos from the event record (they have pT > 0.0 and |eta| < 4.5 at this stage
  const Particles& neutrinos = apply<PromptFinalState>(event, "neutrinos").particlesByPt();
  FourMomentum met;
  for (const Particle& nu : neutrinos) met += nu.momentum();
  if (met.pT() <= 20 * GeV) vetoEvent;

  // Make the plot
  _histo->fill();
}


// Normalise histograms etc., after the run
void finalize() {
  scale(_histo, crossSection() / femtobarn / sumOfWeights());
}

private:

CounterPtr _histo;

};

RIVET_DECLARE_PLUGIN(ATLAS_2015_I1397635);

} ```