Rivet analyses

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

namespace Rivet {


  /// @brief Xi_c+ spectrum
  class ARGUS_1990_I296522 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1990_I296522);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");
      // book histos
      book(_h_obs1, 1, 1, 1);
      book(_h_obs2, 1, 1, 2);
      book(_h_obs3, 1, 1, 3);
      book(_h_all1, 2, 1, 1);
      book(_h_all2, 2, 1, 2);
      book(_h_all3, 2, 1, 3);
      book(_h_x, 3, 1, 1);
    }

    void findDecayProducts(Particle parent, Particles& Xi, Particles& pions, unsigned int& nstable) {
      for (const Particle& p : parent.children()) {
        if (p.abspid() == PID::XIMINUS) {
          Xi.push_back(p);
          ++nstable;
        }
        else if (p.abspid() == PID::PIPLUS) {
          pions.push_back(p);
          ++nstable;
        }
        else if (!p.children().empty())
          findDecayProducts(p, Xi, pions, nstable);
        else
          ++nstable;
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const int idXip = 4232, idXi0 = 4132;
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double Emax = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
      const double Pmax = sqrt(sqr(Emax) - sqr(2.468));
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::abspid == idXip or Cuts::abspid == idXi0)) {
        double xp = p.momentum().p3().mod() / Pmax;
        _h_x->fill(xp);
        Particles Xi, pions;
        unsigned int nstable(0);
        findDecayProducts(p, Xi, pions, nstable);
        if (nstable == 2 && Xi.size() == 1 && pions.size() == 1) {
          _h_obs1->fill(xp);
          _h_all1->fill(xp);
        }
        else if (nstable == 3 && Xi.size() == 1 && pions.size() == 2) {
          _h_obs3->fill(xp);
          _h_all3->fill(xp);
        }
        else if (nstable == 4 && Xi.size() == 1 && pions.size() == 3) {
          _h_obs2->fill(xp);
          _h_all2->fill(xp);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_x);
      scale(_h_obs1, 0.5 * crossSection() / picobarn / sumOfWeights());
      scale(_h_obs2, 0.5 * crossSection() / picobarn / sumOfWeights());
      scale(_h_obs3, 0.5 * crossSection() / picobarn / sumOfWeights());
      scale(_h_all1, crossSection() / picobarn / sumOfWeights());
      scale(_h_all2, crossSection() / picobarn / sumOfWeights());
      scale(_h_all3, crossSection() / picobarn / sumOfWeights());
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_obs1, _h_obs2, _h_obs3, _h_all1, _h_all2, _h_all3;
    Histo1DPtr _h_x;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1990_I296522);

}