Rivet analyses

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

namespace Rivet {


  /// @brief ALEPH pi+-, K+-, p and pbar differential cross-sections at the Z peak
  class ALEPH_1995_I382179 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALEPH_1995_I382179);


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

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

      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(ChargedFinalState(), "FS");

      // Book histograms
      book(_histXpPion,   1, 1, 1);
      book(_histXpKaon,   2, 1, 1);
      book(_histXpProton, 3, 1, 1);

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
      const FinalState& fs = apply<FinalState>(event, "FS");
      if (fs.particles().size() < 2) {
        MSG_DEBUG("Failed ncharged cut");
        vetoEvent;
      }
      MSG_DEBUG("Passed ncharged cut");

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

      for (const Particle& p : fs.particles()) {
        int id = p.abspid();
        // charged pions
        if (id == PID::PIPLUS || id == PID::PIMINUS) {
          _histXpPion->fill(p.p3().mod()/meanBeamMom);
        } else if(id == PID::KPLUS || id == PID::KMINUS) {
          _histXpKaon->fill(p.p3().mod()/meanBeamMom);
        } else if(id == PID::PROTON || id == PID::ANTIPROTON) {
          _histXpProton->fill(p.p3().mod()/meanBeamMom);
        }
      }


    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_histXpPion, 1./sumOfWeights());
      scale(_histXpKaon, 1./sumOfWeights());
      scale(_histXpProton, 1./sumOfWeights());
    }

    /// @}


  private:


    /// @name Histograms
    Histo1DPtr _histXpPion;
    Histo1DPtr _histXpKaon;
    Histo1DPtr _histXpProton;


  };



  RIVET_DECLARE_PLUGIN(ALEPH_1995_I382179);


}