Rivet analyses

title: D0_2009_I815094

$Z/\gamma^*$ + jet + $X$ cross sections differential in pT(jet 1,2,3)

Experiment: D0 (Tevatron Run 2)

Inspire ID: 815094

Status: VALIDATED

Authors: - Frank Siegert

References: - arXiv: 0903.1748

Beams: p- p+

Beam energies: (980.0, 980.0)GeV

Run details: - $p \bar{p} \to e^+ e^-$ + jets at 1960~GeV. Needs mass cut on lepton pair to avoid photon singularity, looser than $65 < m_{ee} < 115$ GeV.

Cross sections as a function of pT of the three leading jets in $Z/\gamma^{*} (\to e^{+} e^{-})$ + jet + X production in $p \bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV, based on an integrated luminosity of 1.0 fb$^{-1}$.

Source code:D0_2009_I815094.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// D0 Z + jet + \f$ X \f$ cross-section / \f$ p_\perp \f$ distributions class D0_2009_I815094 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(D0_2009_I815094);


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

/// Book histograms
void init() {
  // Leptons in constrained tracking acceptance
  Cut cuts = (Cuts::abseta < 1.1 || Cuts::absetaIn(1.5, 2.5)) && Cuts::pT > 25 * GeV;
  DileptonFinder zfinder_constrained(91.2 * GeV, 0.2, cuts && Cuts::abspid == PID::ELECTRON,
                                     Cuts::massIn(65 * GeV, 115 * GeV));
  declare(zfinder_constrained, "DileptonFinderConstrained");
  FastJets conefinder_constrained(zfinder_constrained.remainingFinalState(), JetAlg::D0ILCONE, 0.5);
  declare(conefinder_constrained, "ConeFinderConstrained");

  // Unconstrained leptons
  DileptonFinder zfinder(91.2 * GeV, 0.2, Cuts::abspid == PID::ELECTRON,
                         Cuts::massIn(65 * GeV, 115 * GeV));
  declare(zfinder, "DileptonFinder");
  FastJets conefinder(zfinder.remainingFinalState(), JetAlg::D0ILCONE, 0.5);
  declare(conefinder, "ConeFinder");

  book(_h_jet1_pT_constrained, 1, 1, 1);
  book(_h_jet2_pT_constrained, 3, 1, 1);
  book(_h_jet3_pT_constrained, 5, 1, 1);
  book(_h_jet1_pT, 2, 1, 1);
  book(_h_jet2_pT, 4, 1, 1);
  book(_h_jet3_pT, 6, 1, 1);

  book(_sum_of_weights, "sum_of_weights");
  book(_sum_of_weights_constrained, "sum_of_weights_constrained");
}


// Do the analysis
void analyze(const Event& e) {
  // Unconstrained electrons
  const DileptonFinder& zfinder = apply<DileptonFinder>(e, "DileptonFinder");
  if (zfinder.bosons().size() == 0) {
    MSG_DEBUG("No unique lepton pair found.");
    vetoEvent;
  }
  _sum_of_weights->fill();
  const Jets jets_cut = apply<JetFinder>(e, "ConeFinder")
                            .jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 2.5);
  if (jets_cut.size() > 0) _h_jet1_pT->fill(jets_cut[0].pT() / GeV);
  if (jets_cut.size() > 1) _h_jet2_pT->fill(jets_cut[1].pT() / GeV);
  if (jets_cut.size() > 2) _h_jet3_pT->fill(jets_cut[2].pT() / GeV);


  // Constrained electrons
  const DileptonFinder& zfinder_constrained = apply<DileptonFinder>(e, "DileptonFinderConstrained");
  if (zfinder_constrained.bosons().size() == 0) {
    MSG_DEBUG("No unique constrained lepton pair found.");
    return; // Not really a "veto", since if we got this far there is an unconstrained Z
  }
  _sum_of_weights_constrained->fill();
  const Jets& jets_constrained = apply<JetFinder>(e, "ConeFinderConstrained")
                                     .jetsByPt(Cuts::pT > 20 * GeV);
  /// @todo Replace this explicit selection with a Cut
  Jets jets_cut_constrained;
  for (const Jet& j : jets_constrained) {
    if (j.abseta() < 2.5) jets_cut_constrained.push_back(j);
  }
  if (jets_cut_constrained.size() > 0) _h_jet1_pT_constrained->fill(jets_cut_constrained[0].pT() / GeV);
  if (jets_cut_constrained.size() > 1) _h_jet2_pT_constrained->fill(jets_cut_constrained[1].pT() / GeV);
  if (jets_cut_constrained.size() > 2) _h_jet3_pT_constrained->fill(jets_cut_constrained[2].pT() / GeV);
}


// Finalize
void finalize() {
  scale(_h_jet1_pT, 1 / *_sum_of_weights);
  scale(_h_jet2_pT, 1 / *_sum_of_weights);
  scale(_h_jet3_pT, 1 / *_sum_of_weights);
  scale(_h_jet1_pT_constrained, 1 / *_sum_of_weights_constrained);
  scale(_h_jet2_pT_constrained, 1 / *_sum_of_weights_constrained);
  scale(_h_jet3_pT_constrained, 1 / *_sum_of_weights_constrained);
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_jet1_pT;
Histo1DPtr _h_jet2_pT;
Histo1DPtr _h_jet3_pT;
Histo1DPtr _h_jet1_pT_constrained;
Histo1DPtr _h_jet2_pT_constrained;
Histo1DPtr _h_jet3_pT_constrained;
/// @}

CounterPtr _sum_of_weights, _sum_of_weights_constrained;

};

RIVET_DECLARE_ALIASED_PLUGIN(D0_2009_I815094, D0_2009_S8202443);

} ```

Aliases: - D0_2009_S8202443