D0_2010_S8821313.cc

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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ZFinder.hh"

namespace Rivet {


  class D0_2010_S8821313 : public Analysis {
  public:

    /// Constructor
    D0_2010_S8821313()
      : Analysis("D0_2010_S8821313")
    {    }


    /// @name Analysis methods
    //@{

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

      /// Initialise and register projections
      Cut cuts = (   EtaIn(-3.0, -1.5)
           | EtaIn(-1.1,  1.1)
           | EtaIn( 1.5,  3.0) )
    & (Cuts::pT >= 20.0*GeV);
      FinalState fs; //< @todo Should the eta cuts be on the electrons or the resulting Z? I'd have thought the electrons
      ZFinder zfinder_ee(fs, cuts, PID::ELECTRON, 70*GeV, 110*GeV, 0.2, ZFinder::CLUSTERNODECAY, ZFinder::TRACK);
      addProjection(zfinder_ee, "zfinder_ee");
      ZFinder zfinder_mm(fs, 
             EtaIn(-2.0, 2.0) & (Cuts::pT >= 15.0*GeV),
             PID::MUON, 70*GeV, 110*GeV, 0.0, ZFinder::NOCLUSTER, ZFinder::NOTRACK);
      addProjection(zfinder_mm, "zfinder_mm");

      /// Book histograms here
      _h_phistar_ee.addHistogram(0.0, 1.0, bookHisto1D(1, 1, 1));
      _h_phistar_ee.addHistogram(1.0, 2.0, bookHisto1D(1, 1, 2));
      _h_phistar_ee.addHistogram(2.0, 10.0, bookHisto1D(1, 1, 3));
      _h_phistar_mm.addHistogram(0.0, 1.0, bookHisto1D(2, 1, 1));
      _h_phistar_mm.addHistogram(1.0, 2.0, bookHisto1D(2, 1, 2));
    }


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

      const ZFinder& zfinder_ee = applyProjection<ZFinder>(event, "zfinder_ee");
      if (zfinder_ee.bosons().size() == 1) {
        Particles ee = zfinder_ee.constituents();
        std::sort(ee.begin(), ee.end(), cmpMomByPt);
        const FourMomentum& eminus = PID::threeCharge(ee[0].pdgId()) < 0 ? ee[0].momentum() : ee[1].momentum();
        const FourMomentum& eplus  = PID::threeCharge(ee[0].pdgId()) < 0 ? ee[1].momentum() : ee[0].momentum();
        double phi_acop = M_PI - mapAngle0ToPi(eminus.phi() - eplus.phi());
        double costhetastar = tanh((eminus.eta() - eplus.eta())/2);
        double sin2thetastar = 1 - sqr(costhetastar);
        if (sin2thetastar < 0) sin2thetastar = 0;
        const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
        const FourMomentum& zmom = zfinder_ee.bosons()[0].momentum();
        _h_phistar_ee.fill(zmom.rapidity(), phistar, weight);
      }

      const ZFinder& zfinder_mm = applyProjection<ZFinder>(event, "zfinder_mm");
      if (zfinder_mm.bosons().size() == 1) {
        Particles mm = zfinder_mm.constituents();
        std::sort(mm.begin(), mm.end(), cmpMomByPt);
        const FourMomentum& mminus = PID::threeCharge(mm[0].pdgId()) < 0 ? mm[0].momentum() : mm[1].momentum();
        const FourMomentum& mplus  = PID::threeCharge(mm[0].pdgId()) < 0 ? mm[1].momentum() : mm[0].momentum();
        double phi_acop = M_PI - mapAngle0ToPi(mminus.phi() - mplus.phi());
        double costhetastar = tanh((mminus.eta() - mplus.eta())/2);
        double sin2thetastar = 1 - sqr(costhetastar);
        if (sin2thetastar < 0) sin2thetastar = 0;
        const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
        const FourMomentum& zmom = zfinder_mm.bosons()[0].momentum();
        _h_phistar_mm.fill(zmom.rapidity(), phistar, weight);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      foreach (Histo1DPtr hist, _h_phistar_ee.getHistograms()) normalize(hist);
      foreach (Histo1DPtr hist, _h_phistar_mm.getHistograms()) normalize(hist);
    }

    //@}


  private:

    /// @name Histograms
    //@{
    BinnedHistogram<double> _h_phistar_ee;
    BinnedHistogram<double> _h_phistar_mm;
    //@}


  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(D0_2010_S8821313);

}