// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief psi(2S) -> K+K- eta
class BESIII_2020_I1771616 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1771616);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::pid==100443);
declare(ufs, "UFS");
DecayedParticles psi2S(ufs);
psi2S.addStable(PID::PI0);
psi2S.addStable(PID::K0S);
psi2S.addStable(PID::ETA);
psi2S.addStable(PID::ETAPRIME);
declare(psi2S, "psi2S");
for(unsigned int ix=0;ix<3;++ix)
book(_h[ix],1,1,1+ix);
book(_dalitz, "dalitz",50,0.,11.,50,0.0,11.);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 321,1}, {-321,1}, { 221,1} };
DecayedParticles psi2S = apply<DecayedParticles>(event, "psi2S");
// loop over particles
for(unsigned int ix=0;ix<psi2S.decaying().size();++ix) {
if(!psi2S.modeMatches(ix,3,mode)) continue;
const Particles & eta = psi2S.decayProducts()[ix].at( 221);
const Particles & Kp = psi2S.decayProducts()[ix].at( 321);
const Particles & Km = psi2S.decayProducts()[ix].at(-321);
double mminus = (Km[0].momentum()+eta[0].momentum()).mass2();
double mplus = (Kp[0].momentum()+eta[0].momentum()).mass2();
double mneut = (Kp[0].momentum()+Km [0].momentum()).mass2();
_h[0]->fill(sqrt(mneut ));
_h[1]->fill(sqrt(mplus ));
_h[2]->fill(sqrt(mminus));
_dalitz->fill(mplus,mminus);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<3;++ix)
normalize(_h[ix]);
normalize(_dalitz);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[3];
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2020_I1771616);
}