Rivet analyses

title: ATLAS_2015_CONF_2015_041

$Z$+jets at 13 TeV

Experiment: ATLAS (LHC)

Inspire ID: 1391399

Status: OBSOLETE

Authors: - Christian Gutschow

References: - Expt page: ATLAS-CONF-2015-041

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - Inclusive $Z$ production in the electron channel

Preliminary measurements of the cross-section for the production of a $Z$ boson in association with jets in $pp$ collisions at $\sqrt{s} = 13$\,TeV are presented, using data corresponding to an integrated luminosity of $85\,\text{pb}^{-1}$ collected by the ATLAS experiment at the Large Hadron Collider. The cross-sections are measured for events containing a $Z$ boson decaying to electrons or muons and produced in association with up to four jets in the kinematical range of $p_\text{T} > 30$\,GeV and $|y| < 2.5$. Note: this analysis is superseded by ATLAS_2017_I1514251.

Source code:ATLAS_2015_CONF_2015_041.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// Z + jets in pp at 13 TeV /// /// @note This base class contains a "mode" variable for combined, e, and mu channel derived classes class ATLAS_2015_CONF_2015_041 : public Analysis { public:

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

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2015_CONF_2015_041);

/// @}


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


  _mode = 0;
  if (getOption("LMODE") == "EL")
    _mode = 1;
  else if (getOption("LMODE") == "MU")
    _mode = 2;

  Cut cuts = Cuts::pT > 25 * GeV && Cuts::abseta < 2.5;
  DileptonFinder eefinder(91.2 * GeV, 0.1, cuts && Cuts::abspid == PID::ELECTRON,
                          Cuts::massIn(66 * GeV, 116 * GeV));
  DileptonFinder mmfinder(91.2 * GeV, 0.1, cuts && Cuts::abspid == PID::MUON,
                          Cuts::massIn(66 * GeV, 116 * GeV));
  declare(eefinder, "eefinder");
  declare(mmfinder, "mmfinder");

  // Define veto FS in order to prevent Z-decay products entering the jet algorithm
  VetoedFinalState had_fs;
  had_fs.addVetoOnThisFinalState(eefinder);
  had_fs.addVetoOnThisFinalState(mmfinder);
  FastJets jets(had_fs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::DECAY);
  declare(jets, "jets");

  // combination
  book(_h["Njets_comb"], 1, 1, 1);
  book(_e["ratio_comb"], 2, 1, 1);
  // individual channels
  if (_mode == 0 || _mode == 1) {
    book(_h["Njets_el"], 1, 2, 1);
    book(_e["ratio_el"], 2, 2, 1);
  }
  if (_mode == 0 || _mode == 2) {
    book(_h["Njets_mu"], 1, 2, 2);
    book(_e["ratio_mu"], 2, 2, 2);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  const Particles& elecs = apply<DileptonFinder>(event, "eefinder").constituents();
  const Particles& muons = apply<DileptonFinder>(event, "mmfinder").constituents();

  if (elecs.size() + muons.size() != 2) vetoEvent;

  Jets jets = apply<JetFinder>(event, "jets").jetsByPt(Cuts::pT > 30 * GeV && Cuts::absrap < 2.5);
  idiscardIfAnyDeltaRLess(jets, elecs, 0.4);
  idiscardIfAnyDeltaRLess(jets, muons, 0.4);

  fillHistos(elecs, jets);
  fillHistos(muons, jets);
}

void fillHistos(const Particles& leptons, const Jets& jets) {
  if (leptons.size() != 2) return;

  const size_t njets = jets.size();
  for (size_t i = 0; i <= njets; ++i) {
    if (_mode == 0 || _mode == 1) {
      _h["Njets_comb"]->fill(i + 0.5);
      _h["Njets_el"]->fill(i + 0.5);
    }
    if (_mode == 0 || _mode == 2) {
      _h["Njets_comb"]->fill(i + 0.5);
      _h["Njets_mu"]->fill(i + 0.5);
    }
  }
}

void finalize() {
  scale(_h, crossSectionPerEvent());
  if (_mode == 0) scale(_h["Njets_comb"], 0.5); // average of el + mu

  vector<string> channels = {"comb"};
  if (_mode == 0 || _mode == 1) channels.push_back("el");
  if (_mode == 0 || _mode == 2) channels.push_back("mu");
  YODA::Estimate num, den;
  for (size_t i = 1; i < 5; ++i) {
    for (const string& ch : channels) {
      num.set(_h["Njets_" + ch]->bin(i + 1).sumW(), _h["Njets_" + ch]->bin(i + 1).errW());
      den.set(_h["Njets_" + ch]->bin(i).sumW(), _h["Njets_" + ch]->bin(i).errW());
      _e["ratio_" + ch]->bin(i) = YODA::divide(num, den);
    }
  }
}

/// @}

private:

size_t _mode;

map<string, Estimate1DPtr> _e;
map<string, Histo1DPtr> _h;

};

RIVET_DECLARE_PLUGIN(ATLAS_2015_CONF_2015_041); } ```