// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief eta' -> gamma gamma pi0
class BESIII_2016_I1504943 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1504943);
/// @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);
ETA.addStable(PID::K0S);
declare(ETA, "ETA");
// Book histograms
for(unsigned int ix=0;ix<3;++ix)
book(_h_br[ix],1,1,1+ix);
book(_h_m, 2, 1, 1);
book(_netap, "TMP/netap");
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { {111,1}, { 22,2} };
DecayedParticles ETA = apply<DecayedParticles>(event, "ETA");
// loop over particles
for(unsigned int ix=0;ix<ETA.decaying().size();++ix) {
_netap->fill();
// select right decay mode
if ( !ETA.modeMatches(ix,3,mode)) continue;
const Particles & gam = ETA.decayProducts()[ix].at(22);
double mass2 = (gam[0].momentum()+gam[1].momentum()).mass2();
_h_m->fill(mass2);
_h_br[0]->fill(.5);
if(any(ETA.decaying()[ix].children(), hasAbsPID(PID::OMEGA))) _h_br[1]->fill(.5);
if(ETA.decaying()[ix].children().size()==3) _h_br[2]->fill(0.5);
}
}
/// Normalise histograms etc., after the run
void finalize() {
// eta' width in kev
double gammaEtap = 0.188e3;
scale(_h_m, gammaEtap/ *_netap);
for(unsigned int ix=0;ix<3;++ix)
scale(_h_br[ix], 1e4/ *_netap);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_m,_h_br[3];
CounterPtr _netap;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2016_I1504943);
}