// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief eta' -> pions
class BESIII_2017_I1469067 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1469067);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::pid==PID::ETAPRIME);
declare(ufs, "UFS");
DecayedParticles ETA(ufs);
ETA.addStable(PID::PI0);
ETA.addStable(PID::K0S);
ETA.addStable(PID::ETA);
declare(ETA, "ETA");
// histograms
for(unsigned int ix=0;ix<4;++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 = { {211,1}, {-211,1}, {111,1} };
static const map<PdgId,unsigned int> & mode2 = { {111,3} };
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,mode1)) {
const Particle & pi0 = ETA.decayProducts()[ix].at( 111)[0];
const Particle & pip = ETA.decayProducts()[ix].at( 211)[0];
const Particle & pim = ETA.decayProducts()[ix].at(-211)[0];
_h[0]->fill((pip.momentum()+pim.momentum()).mass());
_h[1]->fill((pip.momentum()+pi0.momentum()).mass());
_h[2]->fill((pim.momentum()+pi0.momentum()).mass());
}
else if ( ETA.modeMatches(ix,3,mode2)) {
const Particles & pi0 = ETA.decayProducts()[ix].at(111);
for(unsigned int ix=0;ix<3;++ix) {
for(unsigned int iy=ix+1;iy<3;++iy)
_h[3]->fill((pi0[ix].momentum()+pi0[iy].momentum()).mass());
}
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
// normalize the histograms
for(unsigned int ix=0;ix<4;++ix)
normalize(_h[ix]);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[4];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2017_I1469067);
}