Rivet analyses

Z+jets angular distributions

Experiment: D0 (Tevatron Run 2)

Inspire ID: 826756

Status: VALIDATED

Authors: - Frank Siegert

References: - arXiv: 0907.4286

Beams: p- p+

Beam energies: (980.0, 980.0)GeV

Run details: - pp̄ → μ⁺μ⁻ + jets at 1960~GeV. Needs mass cut on lepton pair to avoid photon singularity, looser than 65 < m_ee < 115 GeV.

First measurements at a hadron collider of differential cross sections for Z( → μμ)+jet+X production in Δϕ(Z, j), |Δy(Z, j)| and |y_boost(Z, j)|. Vector boson production in association with jets is an excellent probe of QCD and constitutes the main background to many small cross section processes, such as associated Higgs production. These measurements are crucial tests of the predictions of perturbative QCD and current event generators, which have varied success in describing the data. Using these measurements as inputs in tuning event generators will increase the experimental sensitivity to rare signals.

Source code:`D0_2009_I826756.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/DileptonFinder.hh"
#include "Rivet/Projections/FastJets.hh"

namespace Rivet {


  /// D0 Z+jets angular distributions
  class D0_2009_I826756 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(D0_2009_I826756);


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

    /// Book histograms
    void init() {
      Cut cut = Cuts::abseta < 1.7 && Cuts::pT > 15*GeV;
      DileptonFinder zfinder(91.2*GeV, 0.2, cut && Cuts::abspid == PID::MUON, Cuts::massIn(65*GeV, 115*GeV));
      declare(zfinder, "DileptonFinder");

      FastJets conefinder(zfinder.remainingFinalState(), JetAlg::D0ILCONE, 0.5);
      declare(conefinder, "ConeFinder");

      book(_h_dphi_jet_Z25 ,1, 1, 1);
      book(_h_dphi_jet_Z45 ,2, 1, 1);

      book(_h_dy_jet_Z25 ,3, 1, 1);
      book(_h_dy_jet_Z45 ,4, 1, 1);

      book(_h_yboost_jet_Z25 ,5, 1, 1);
      book(_h_yboost_jet_Z45 ,6, 1, 1);

      book(_h_dphi_jet_Z25_xs ,1, 1, 2);
      book(_h_dphi_jet_Z45_xs ,2, 1, 2);

      book(_h_dy_jet_Z25_xs ,3, 1, 2);
      book(_h_dy_jet_Z45_xs ,4, 1, 2);

      book(_h_yboost_jet_Z25_xs ,5, 1, 2);
      book(_h_yboost_jet_Z45_xs ,6, 1, 2);

      book(_inclusive_Z_sumofweights, "_inclusive_Z_sumofweights");
    }


    void analyze(const Event& event) {
      const DileptonFinder& zfinder = apply<DileptonFinder>(event, "DileptonFinder");
      if (zfinder.bosons().size() == 1) {
        // count inclusive sum of weights for histogram normalisation
        _inclusive_Z_sumofweights->fill();

        const FourMomentum& zmom = zfinder.bosons()[0].momentum();
        if (zmom.pT() < 25*GeV) vetoEvent;

        Jets jets = apply<JetFinder>(event, "ConeFinder").jetsByPt(Cuts::pT > 20*GeV && Cuts::abseta < 2.8);

        // Return if there are no jets:
        if (jets.size() < 1) {
          MSG_DEBUG("Skipping event " << numEvents() << " because no jets pass cuts ");
          vetoEvent;
        }

        const FourMomentum& jetmom = jets[0].momentum();
        const double yZ = zmom.rapidity();
        const double yjet = jetmom.rapidity();
        const double dphi = deltaPhi(zmom, jetmom);
        const double dy = deltaRap(zmom, jetmom);
        const double yboost = fabs(yZ+yjet)/2;

        if (zmom.pT() > 25*GeV) {
          _h_dphi_jet_Z25->fill(dphi);
          _h_dy_jet_Z25->fill(dy);
          _h_yboost_jet_Z25->fill(yboost);
          _h_dphi_jet_Z25_xs->fill(dphi);
          _h_dy_jet_Z25_xs->fill(dy);
          _h_yboost_jet_Z25_xs->fill(yboost);
        }
        if (zmom.pT() > 45*GeV) {
          _h_dphi_jet_Z45->fill(dphi);
          _h_dy_jet_Z45->fill(dy);
          _h_yboost_jet_Z45->fill(yboost);
          _h_dphi_jet_Z45_xs->fill(dphi);
          _h_dy_jet_Z45_xs->fill(dy);
          _h_yboost_jet_Z45_xs->fill(yboost);
        }
      }

    }


    void finalize() {
      if (_inclusive_Z_sumofweights->val() == 0) return;
      scale(_h_dphi_jet_Z25, 1/ *_inclusive_Z_sumofweights);
      scale(_h_dphi_jet_Z45, 1/ *_inclusive_Z_sumofweights);
      scale(_h_dy_jet_Z25, 1/ *_inclusive_Z_sumofweights);
      scale(_h_dy_jet_Z45, 1/ *_inclusive_Z_sumofweights);
      scale(_h_yboost_jet_Z25, 1/ *_inclusive_Z_sumofweights);
      scale(_h_yboost_jet_Z45, 1/ *_inclusive_Z_sumofweights);

      scale(_h_dphi_jet_Z25_xs, crossSectionPerEvent());
      scale(_h_dphi_jet_Z45_xs, crossSectionPerEvent());
      scale(_h_dy_jet_Z25_xs, crossSectionPerEvent());
      scale(_h_dy_jet_Z45_xs, crossSectionPerEvent());
      scale(_h_yboost_jet_Z25_xs, crossSectionPerEvent());
      scale(_h_yboost_jet_Z45_xs, crossSectionPerEvent());
    }

    /// @}


  private:

    /// @name Histograms (normalised)
    /// @{
    Histo1DPtr _h_dphi_jet_Z25;
    Histo1DPtr _h_dphi_jet_Z45;

    Histo1DPtr _h_dy_jet_Z25;
    Histo1DPtr _h_dy_jet_Z45;

    Histo1DPtr _h_yboost_jet_Z25;
    Histo1DPtr _h_yboost_jet_Z45;
    /// @}

    /// @name Histograms (absolute cross sections)
    /// @{
    Histo1DPtr _h_dphi_jet_Z25_xs;
    Histo1DPtr _h_dphi_jet_Z45_xs;

    Histo1DPtr _h_dy_jet_Z25_xs;
    Histo1DPtr _h_dy_jet_Z45_xs;

    Histo1DPtr _h_yboost_jet_Z25_xs;
    Histo1DPtr _h_yboost_jet_Z45_xs;
    /// @}

    CounterPtr _inclusive_Z_sumofweights;

  };



  RIVET_DECLARE_ALIASED_PLUGIN(D0_2009_I826756, D0_2009_S8349509);

}

Aliases: - D0_2009_S8349509

Rivet analyses

Z+jets angular distributions

Source code:D0_2009_I826756.cc

Source code:`D0_2009_I826756.cc`