Rivet analyses

title: MC_ZJETS

Monte Carlo validation observables for $Z[\ell^+ \, \ell^-]$ + jets production

Experiment: ()

Status: VALIDATED

Authors: - Frank Siegert - Christian Gutschow

References: none listed

Beams: * *

Beam energies: ANY

Run details: - $\ell^+ \ell^-$ + jets analysis. Needs mass cut on lepton pair to avoid photon singularity, e.g. a min range of $66 < m_{ll} < 116$ GeV

Available observables are the pT of jets 1-4, jet multiplicity, $\Delta\eta(Z, \text{jet1})$, $\Delta R(\text{jet2}, \text{jet3})$, differential jet rates 0->1, 1->2, 2->3, 3->4, and integrated 0--4 jet rates.

Source code:MC_ZJETS.cc

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

include "Rivet/Analyses/MC_JETS_BASE.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FastJets.hh"

namespace Rivet {

/// @brief MC validation analysis for Z + jets events class MC_ZJETS : public MC_JETS_BASE { public:

/// Default constructor
MC_ZJETS(string name = "MC_ZJETS")
    : MC_JETS_BASE(name, 4, "Jets") { }


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

/// Initialize
void init() {
  _dR = 0.2;
  if (getOption("SCHEME") == "BARE") _dR = 0.0;
  _lepton = PID::ELECTRON;
  if (getOption("LMODE") == "MU") _lepton = PID::MUON;

  // set FS cuts from input options
  const double etacut = getOption<double>("ABSETALMAX", 3.5);
  const double ptcut = getOption<double>("PTLMIN", 25.);

  Cut cut = Cuts::abseta < etacut && Cuts::pT > ptcut * GeV;
  DileptonFinder zfinder(91.2 * GeV, _dR, cut && Cuts::abspid == _lepton,
                         Cuts::massIn(66.0 * GeV, 116.0 * GeV));
  declare(zfinder, "DileptonFinder");

  // set ptcut from input option
  const double jetptcut = getOption<double>("PTJMIN", 20.0);
  _jetptcut = jetptcut * GeV;

  // set clustering radius from input option
  const double R = getOption<double>("R", 0.4);

  // set clustering algorithm from input option
  JetAlg clusterAlgo;
  const string algoopt = getOption("ALGO", "ANTIKT");
  if (algoopt == "KT") {
    clusterAlgo = JetAlg::KT;
  }
  else if (algoopt == "CA") {
    clusterAlgo = JetAlg::CA;
  }
  else if (algoopt == "ANTIKT") {
    clusterAlgo = JetAlg::ANTIKT;
  }
  else {
    MSG_WARNING("Unknown jet clustering algorithm option " + algoopt + ". Defaulting to anti-kT");
    clusterAlgo = JetAlg::ANTIKT;
  }

  FastJets jetpro(zfinder.remainingFinalState(), clusterAlgo, R);
  declare(jetpro, "Jets");

  book(_h_Z_jet1_deta, "Z_jet1_deta", 50, -5, 5);
  book(_h_Z_jet1_dR, "Z_jet1_dR", 25, 0.5, 7.0);

  MC_JETS_BASE::init();
}


/// Do the analysis
void analyze(const Event& e) {
  MSG_TRACE("MC_ZJETS: running DileptonFinder");
  const DileptonFinder& zfinder = apply<DileptonFinder>(e, "DileptonFinder");
  if (zfinder.bosons().size() != 1) vetoEvent;
  const FourMomentum& zmom = zfinder.bosons()[0].momentum();
  MSG_TRACE("MC_ZJETS: have exactly one Z boson candidate");

  const Jets& jets = apply<FastJets>(e, "Jets").jetsByPt(Cuts::pT > _jetptcut);
  if (jets.size() > 0) {
    MSG_TRACE("MC_ZJETS: have at least one valid jet");
    _h_Z_jet1_deta->fill(zmom.eta() - jets[0].eta());
    _h_Z_jet1_dR->fill(deltaR(zmom, jets[0].momentum()));
  }

  MC_JETS_BASE::analyze(e);
}


/// Finalize
void finalize() {
  scale(_h_Z_jet1_deta, crossSection() / picobarn / sumOfWeights());
  scale(_h_Z_jet1_dR, crossSection() / picobarn / sumOfWeights());
  MC_JETS_BASE::finalize();
}

/// @}

protected:

/// @name Parameters for specialised e/mu and dressed/bare subclassing
/// @{
double _dR;
PdgId _lepton;
/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_Z_jet1_deta;
Histo1DPtr _h_Z_jet1_dR;
/// @}

};

RIVET_DECLARE_PLUGIN(MC_ZJETS);

} ```