// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief eta' -> pi+pi- gamma decays
class CRYSTAL_BARREL_1997_I456942 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CRYSTAL_BARREL_1997_I456942);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::pid==331);
declare(ufs, "UFS");
DecayedParticles ETA(ufs);
ETA.addStable(PID::PI0);
declare(ETA, "ETA");
// Book histograms
book(_h_m, 1, 1, 1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { {211,1}, {-211,1}, { 22,1} };
// Loop over eta' mesons
DecayedParticles ETA = apply<DecayedParticles>(event, "ETA");
// loop over particles
for(unsigned int ix=0;ix<ETA.decaying().size();++ix) {
// select right decay mode
if ( !ETA.modeMatches(ix,3,mode)) continue;
const Particle & pip = ETA.decayProducts()[ix].at( 211)[0];
const Particle & pim = ETA.decayProducts()[ix].at(-211)[0];
_h_m->fill((pip.momentum()+pim.momentum()).mass()/MeV);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_m,1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_m;
/// @}
};
RIVET_DECLARE_PLUGIN(CRYSTAL_BARREL_1997_I456942);
}