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ATLAS_2010_S8919674

$W$ + jets jet multiplicities and $p_\perp$
Experiment: ATLAS (LHC)
Inspire ID: 882534
Status: VALIDATED
Authors:
  • Frank Siegert
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • W+jets events ideally with matrix element corrections to describe the higher jet multiplicities correctly. Both channels, electron and muon, are part of this analysis and should be run simultaneously.

Cross sections, in both the electron and muon decay modes of the W boson, are presented as a function of jet multiplicity and of the transverse momentum of the leading and next-to-leading jets in the event. Measurements are also presented of the ratio of cross sections for inclusive jet multiplicities. The results, based on an integrated luminosity of 1.3 pb-1, have been corrected for all known detector effects and are quoted in a limited and well-defined range of jet and lepton kinematics.

Source code: ATLAS_2010_S8919674.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/WFinder.hh"

namespace Rivet {


  /// W + jets jet multiplicities and pT
  class ATLAS_2010_S8919674 : public Analysis {
  public:

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

    /// Constructor
    ATLAS_2010_S8919674()
      : Analysis("ATLAS_2010_S8919674")
    {    }

    //@}


  public:

    /// @name Analysis methods
    //@{

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

      // Set up projections to find the electron and muon Ws
      FinalState fs;
      Cut cuts = (Cuts::abseta < 1.37 || Cuts::absetaIn(1.52, 2.47)) && Cuts::pT > 20*GeV;
      WFinder wfinder_e(fs, cuts, PID::ELECTRON, 0*GeV, 1000*GeV, 25*GeV);
      declare(wfinder_e, "W_e");
      WFinder wfinder_mu(fs, Cuts::abseta < 2.4 && Cuts::pT > 20*GeV, PID::MUON, 0*GeV, 1000*GeV, 25*GeV);
      declare(wfinder_mu, "W_mu");

      // Input for the jets: no neutrinos, no muons, and no electron which passed the electron cuts
      VetoedFinalState veto;
      veto.addVetoOnThisFinalState(wfinder_e);
      veto.addVetoOnThisFinalState(wfinder_mu);
      veto.addVetoPairId(PID::MUON);
      veto.vetoNeutrinos();
      FastJets jets(veto, FastJets::ANTIKT, 0.4);
      declare(jets, "jets");

      /// Book histograms
      _h_el_njet_inclusive = bookHisto1D(1,1,1);
      _h_mu_njet_inclusive = bookHisto1D(2,1,1);
      _h_el_pT_jet1 = bookHisto1D(5,1,1);
      _h_mu_pT_jet1 = bookHisto1D(6,1,1);
      _h_el_pT_jet2 = bookHisto1D(7,1,1);
      _h_mu_pT_jet2 = bookHisto1D(8,1,1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const double weight = event.weight();

      const Jets& jets = apply<FastJets>(event, "jets").jetsByPt(20.0*GeV);

      const WFinder& We = apply<WFinder>(event, "W_e");
      if (We.bosons().size() == 1) {
        const FourMomentum p_miss = We.constituentNeutrinos()[0];
        const FourMomentum p_lept = We.constituentLeptons()[0];
        if (p_miss.Et() > 25*GeV && We.mT() > 40*GeV) {
          Jets js;
          for (const Jet& j : jets) {
            if (j.abseta() < 2.8 && deltaR(p_lept, j.momentum()) > 0.5)
              js.push_back(j);
          }
          _h_el_njet_inclusive->fill(0, weight);
          if (js.size() >= 1) {
            _h_el_njet_inclusive->fill(1, weight);
            _h_el_pT_jet1->fill(js[0].pT(), weight);
          }
          if (js.size() >= 2) {
            _h_el_njet_inclusive->fill(2, weight);
            _h_el_pT_jet2->fill(js[1].pT(), weight);
          }
          if (js.size() >= 3) {
            _h_el_njet_inclusive->fill(3, weight);
          }
        }
      }

      const WFinder& Wm = apply<WFinder>(event, "W_mu");
      if (Wm.bosons().size() == 1) {
        const FourMomentum p_miss = Wm.constituentNeutrinos()[0];
        const FourMomentum p_lept = Wm.constituentLeptons()[0];
        if (p_miss.Et() > 25*GeV && Wm.mT() > 40*GeV) {
          Jets js;
          for (const Jet& j : jets) {
            if (j.abseta() < 2.8 && deltaR(p_lept, j.momentum()) > 0.5)
              js.push_back(j);
          }
          _h_mu_njet_inclusive->fill(0, weight);
          if (js.size() >= 1) {
            _h_mu_njet_inclusive->fill(1, weight);
            _h_mu_pT_jet1->fill(js[0].pT(), weight);
          }
          if (js.size() >= 2) {
            _h_mu_njet_inclusive->fill(2, weight);
            _h_mu_pT_jet2->fill(js[1].pT(), weight);
          }
          if (js.size() >= 3) {
            _h_mu_njet_inclusive->fill(3, weight);
          }
          if (js.size() >= 4) {
            _h_mu_njet_inclusive->fill(4, weight);
          }
        }
      }

    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double normfac = crossSection()/sumOfWeights();
      scale(_h_el_njet_inclusive, normfac);
      scale(_h_mu_njet_inclusive, normfac);
      scale(_h_el_pT_jet1, normfac);
      scale(_h_mu_pT_jet1, normfac);
      scale(_h_el_pT_jet2, normfac);
      scale(_h_mu_pT_jet2, normfac);
    }

    //@}


  private:

    /// @name Histograms
    //@{

    Histo1DPtr _h_el_njet_inclusive;
    Histo1DPtr _h_mu_njet_inclusive;
    Histo1DPtr _h_el_pT_jet1;
    Histo1DPtr _h_mu_pT_jet1;
    Histo1DPtr _h_el_pT_jet2;
    Histo1DPtr _h_mu_pT_jet2;
    //@}

  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2010_S8919674);

}