Rivet analyses

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

namespace Rivet {


  /// @brief B -> eta K gamma
  class BABAR_2009_I785439 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I785439);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(PID::ETA);
      BB.addStable(PID::K0S);
      declare(BB, "BB");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1, 1, 1 + ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{221, 1}, {310, 1}, {22, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{221, 1}, {321, 1}, {22, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{221, 1}, {-321, 1}, {22, 1}};
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      // loop over particles
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        int imode = 0, sign = 1;
        if (BB.decaying()[ix].abspid() == 511) {
          imode = 1;
          if (!BB.modeMatches(ix, 3, mode1)) continue;
        }
        else {
          imode = 0;
          if (BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode2)) {
            sign = 1;
          }
          else if (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode2CC)) {
            sign = -1;
          }
          else
            continue;
        }
        const Particle& KK = BB.decayProducts()[ix].at(imode == 0 ? sign * 321 : 310)[0];
        const Particle& eta = BB.decayProducts()[ix].at(221)[0];
        _h[imode]->fill((KK.momentum() + eta.momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h[ix], 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2009_I785439);

}