Rivet analyses

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

namespace Rivet {


  /// @brief D0 -> KS0 pi+ pi-
  class CLEO_2003_I633196 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_2003_I633196);


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

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

      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 421);
      declare(ufs, "UFS");
      DecayedParticles D0(ufs);
      D0.addStable(PID::PI0);
      D0.addStable(PID::K0S);
      D0.addStable(PID::ETA);
      D0.addStable(PID::ETAPRIME);
      declare(D0, "D0");

      // Histograms
      book(_h_Kpim, 1, 1, 1);
      book(_h_pipi, 1, 1, 2);
      book(_h_Kpip, 1, 1, 3);
      book(_dalitz, "dalitz", 50, 0., 3., 50, 0., 2.);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId, unsigned int>& mode = {{310, 1}, {211, 1}, {-211, 1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
        if (!D0.modeMatches(ix, 3, mode)) continue;
        int sign = D0.decaying()[ix].pid() / 421;
        const Particles& pip = D0.decayProducts()[ix].at(sign * 211);
        const Particles& pim = D0.decayProducts()[ix].at(-sign * 211);
        const Particles& K0 = D0.decayProducts()[ix].at(310);
        double mminus = (pim[0].momentum() + K0[0].momentum()).mass2();
        double mplus = (pip[0].momentum() + K0[0].momentum()).mass2();
        double mpipi = (pip[0].momentum() + pim[0].momentum()).mass2();
        _h_Kpip->fill(mplus);
        _h_Kpim->fill(mminus);
        _h_pipi->fill(mpipi);
        _dalitz->fill(mminus, mpipi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_Kpip);
      normalize(_h_pipi);
      normalize(_h_Kpim);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kpim, _h_pipi, _h_Kpip;
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CLEO_2003_I633196);

}