Rivet analyses

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

namespace Rivet {


  /// @brief Xi_c*+ spectrum
  class CLEOII_1996_I416471 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1996_I416471);


    /// @name Analysis methods
    /// @{
    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");
      // book histos
      book(_h_x, 2, 1, 1);
      book(_r, 3, 1, 1);
      book(_c_xi, "TMP/c_xi");
    }

    // Check for explicit decay into pdgids
    bool isDecay(const Particle& mother, vector<int> ids) {
      if (mother.pid() < 0) {
        for (unsigned int ix = 0; ix < ids.size(); ++ix) ids[ix] *= -1;
      }
      // Trivial check to ignore any other decays but the one in question modulo photons
      const Particles children = mother.children(Cuts::pid != PID::PHOTON);
      if (children.size() != ids.size()) return false;
      // Check for the explicit decay
      return all(ids, [&](int i) { return count(children, hasPID(i)) == 1; });
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const int idXi = 4324;
      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(2.645));
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::abspid == idXi)) {
        double xp = p.momentum().p3().mod() / Pmax;
        _h_x->fill(xp);
        int sign = p.pid() / p.abspid();
        if (isDecay(p, {sign * 4132, sign * 211})) {
          _r->fill("10.58"s);
        }
      }
      unsigned int nxi = ufs.particles(Cuts::abspid == 4132).size();
      _c_xi->fill(nxi);
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_x, 1, false);
      scale(_r, 1. / *_c_xi);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_x;
    BinnedHistoPtr<string> _r;
    CounterPtr _c_xi;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CLEOII_1996_I416471);

}