ALEPH_1999_S4193598.cc

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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableFinalState.hh"

namespace Rivet {

  class ALEPH_1999_S4193598 : public Analysis {
  public:

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

    /// Constructor
    ALEPH_1999_S4193598()
      : Analysis("ALEPH_1999_S4193598")
    {
      _sumWpassed = 0.0;
    }

    //@}


  public:

    /// Book histograms and initialise projections before the run
    void init() {
      addProjection(Beam(), "Beams");
      addProjection(UnstableFinalState(), "UFS");
      addProjection(ChargedFinalState(), "CFS");

      _h_Xe_Ds = bookHisto1D(1, 1, 1);
    }


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

      // Trigger condition
      const ChargedFinalState& cfs = applyProjection<ChargedFinalState>(event, "CFS");
      if (cfs.size() < 5) vetoEvent;

      _sumWpassed += weight;

      const UnstableFinalState& ufs = applyProjection<UnstableFinalState>(event, "UFS");

      // Get beams and average beam momentum
      const ParticlePair& beams = applyProjection<Beam>(event, "Beams").beams();
      const double meanBeamMom = ( beams.first.p3().mod() +
                                   beams.second.p3().mod() ) / 2.0/GeV;

      foreach (const Particle& p, ufs.particles()) {
        const PdgId pid = p.abspid();

        switch (pid) {
        case 413:

          // Accept all D*+- decays. Normalisation to D0 + pi+- in finalize()

          // Scaled energy.
          const double energy = p.E()/GeV;
          const double scaledEnergy = energy/meanBeamMom;
          _h_Xe_Ds->fill(scaledEnergy, weight);

          break;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      // Scale to the product of branching fractions D0*->D0 pi  x  D0->Kpi(charged)
      // Numbers are taken from PDG 2010
      scale(_h_Xe_Ds, 0.677*0.0389/_sumWpassed);

    }

  private:
    double _sumWpassed;

  private:

    Histo1DPtr _h_Xe_Ds;

  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ALEPH_1999_S4193598);

}