// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief J/psi -> gamma eta' pi+pi-
class BESIII_2016_I1437949 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1437949);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==443);
declare(ufs, "UFS");
DecayedParticles PSI(ufs);
PSI.addStable(PID::ETA);
PSI.addStable(PID::ETAPRIME);
declare(PSI, "PSI");
// histos
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1,1,1+ix);
book(_h[2],2,1,1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// find the J/psi decays
static const map<PdgId,unsigned int> & mode = { { 22,1}, { 331,1}, {211,1}, {-211,1}};
DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
for(unsigned int ix=0;ix<PSI.decaying().size();++ix) {
if(!PSI.modeMatches(ix,4,mode)) continue;
const Particle & gam = PSI.decayProducts()[ix].at( 22)[0];
double mass =(PSI.decaying()[ix].momentum()-gam.momentum()).mass() ;
for(unsigned int ix=0;ix<3;++ix) _h[ix]->fill(mass);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<3;++ix)
normalize(_h[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2016_I1437949);
}