Rivet analyses

title: ATLAS_2013_I1217867

kT splitting scales in W->lv events

Experiment: ATLAS (LHC)

Inspire ID: 1217867

Status: VALIDATED

Authors: - Frank Siegert

References: - Expt page: ATLAS-STDM-2012-12 - arXiv: 1302.1415

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - W+jet events in the electron and/or the muon decay channel.

Cluster splitting scales are measured in events containing W bosons decaying to electrons or muons. The measurement comprises the four hardest splitting scales in a kT cluster sequence of the hadronic activity accompanying the W boson, and ratios of these splitting scales.

Source code:ATLAS_2013_I1217867.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

class ATLAS_2013_I1217867 : public Analysis { public:

/// @name Constructors etc.
/// @{

/// Constructor
ATLAS_2013_I1217867()
    : Analysis("ATLAS_2013_I1217867") {
  m_njet = 4;
  _h_dI.resize(2, std::vector<Histo1DPtr>(m_njet));
  _h_dI_ratio.resize(2, std::vector<Histo1DPtr>(m_njet - 1));
}

/// @}

public:

/// @name Analysis methods
/// @{

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

  FinalState fs(Cuts::abseta < 5.0);

  Cut cuts = (Cuts::absetaIn(0, 1.37) || Cuts::absetaIn(1.52, 2.47)) && Cuts::pT > 20 * GeV;
  LeptonFinder electronClusters(0.1, Cuts::abspid == PID::ELECTRON && cuts);
  declare(electronClusters, "electronClusters");

  Cut mucuts = Cuts::abseta < 2.4 && Cuts::pT > 20 * GeV;
  LeptonFinder muonClusters(0.1, Cuts::abspid == PID::MUON && mucuts);
  declare(muonClusters, "muonClusters");

  IdentifiedFinalState neutrinos(Cuts::pT > 25 * GeV);
  neutrinos.acceptNeutrinos();
  declare(neutrinos, "neutrinos");

  VetoedFinalState jetFS(fs);
  jetFS.addVetoOnThisFinalState(electronClusters);
  jetFS.addVetoOnThisFinalState(muonClusters);
  jetFS.addVetoOnThisFinalState(neutrinos);
  FastJets jetpro(jetFS, JetAlg::KT, 0.6, JetMuons::ALL, JetInvisibles::DECAY);
  declare(jetpro, "jets");

  // Book histograms
  for (size_t flav = 0; flav < 2; ++flav) {
    for (size_t i = 0; i < m_njet; ++i) book(_h_dI[flav][i], i + 1, 1, flav + 1);
    for (size_t i = 0; i < m_njet - 1; ++i) book(_h_dI_ratio[flav][i], 4 + i + 1, 1, flav + 1);
  }
}


/// Perform the per-event analysis
void analyze(const Event& e) {
  const LeptonFinder& electronClusters = apply<LeptonFinder>(e, "electronClusters");
  const LeptonFinder& muonClusters = apply<LeptonFinder>(e, "muonClusters");
  int ne = electronClusters.dressedLeptons().size();
  int nmu = muonClusters.dressedLeptons().size();

  FourMomentum lepton;
  size_t flav = 2;
  if (ne == 1) {
    lepton = electronClusters.dressedLeptons()[0].momentum();
    flav = 0;
    if (nmu > 0) vetoEvent;
  }
  else if (nmu == 1) {
    lepton = muonClusters.dressedLeptons()[0].momentum();
    flav = 1;
    if (ne > 0) vetoEvent;
  }
  else {
    vetoEvent;
  }

  const Particles& neutrinos = apply<FinalState>(e, "neutrinos").particlesByPt();
  if (neutrinos.size() < 1) vetoEvent;
  FourMomentum neutrino = neutrinos[0].momentum();

  double mtW = sqrt(2.0 * lepton.pT() * neutrino.pT() * (1 - cos(lepton.phi() - neutrino.phi())));
  if (mtW < 40.0 * GeV) vetoEvent;

  const shared_ptr<fastjet::ClusterSequence> seq = apply<FastJets>(e, "jets").clusterSeq();
  if (seq) {
    for (size_t i = 0; i < min(m_njet, (size_t)seq->n_particles()); ++i) {
      double d_ij = sqrt(seq->exclusive_dmerge_max(i));
      _h_dI[flav][i]->fill(d_ij);

      if (i < m_njet - 1) {
        if (d_ij > 20.0 * GeV) {
          double d_ijplus1 = sqrt(seq->exclusive_dmerge_max(i + 1));
          _h_dI_ratio[flav][i]->fill(d_ijplus1 / d_ij);
        }
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (size_t flav = 0; flav < 2; ++flav) {
    for (size_t i = 0; i < m_njet; ++i) {
      normalize(_h_dI[flav][i], 1.0, false);
      if (i < m_njet - 1) normalize(_h_dI_ratio[flav][i], 1.0, false);
    }
  }
}

/// @}

private:

/// @name Histograms
/// @{
vector<vector<Histo1DPtr>> _h_dI;
vector<vector<Histo1DPtr>> _h_dI_ratio;
/// @}

size_t m_njet;

};

RIVET_DECLARE_PLUGIN(ATLAS_2013_I1217867);

} ```