// -*- 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_2022_I2018236 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2018236);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::pid==443);
declare(ufs, "UFS");
DecayedParticles psi(ufs);
psi.addStable(PID::PI0);
psi.addStable(PID::K0S);
psi.addStable(PID::ETA);
psi.addStable(PID::ETAPRIME);
declare(psi, "psi");
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
for(unsigned int iz=1;iz<2;++iz)
book(_h[ix][iy][iz],1+ix,1+iy,1+iz);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 211,1}, {-211,1}, { 331,1} ,{22,1} };
DecayedParticles psi = apply<DecayedParticles>(event, "psi");
// loop over particles
for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
if(!psi.modeMatches(ix,4,mode)) continue;
const Particle & eta = psi.decayProducts()[ix].at( 331)[0];
const Particle & pip = psi.decayProducts()[ix].at( 211)[0];
const Particle & pim = psi.decayProducts()[ix].at(-211)[0];
double m1 = (pip.momentum()+pim.momentum()+eta.momentum()).mass();
double m2 = (pip.momentum()+pim.momentum()).mass();
for(unsigned int ix=0;ix<2;++ix) {
_h[0][ix][1]->fill(m1);
_h[1][ix][1]->fill(m2);
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
for(unsigned int iz=1;iz<2;++iz)
normalize(_h[ix][iy][iz],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2][2][2];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2022_I2018236);
}