// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief J/psi psi(2S) -> p pbar eta'
class BESIII_2019_I1709205 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1709205);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::pid==443 or Cuts::pid==100443);
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<6;++iy) {
book(_h[ix][iy],1+ix,1,1+iy);
}
}
book(_dalitz[0], "dalitz_1",50,3.,8.,50,3.,8.);
book(_dalitz[1], "dalitz_2",50,3.5,5.,50,3.5,5.);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 2212,1}, {-2212,1}, { 331,1} };
DecayedParticles psi = apply<DecayedParticles>(event, "psi");
// loop over particles
for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
if(!psi.modeMatches(ix,3,mode)) continue;
const Particles & etap = psi.decayProducts()[ix].at( 331);
const Particles & pp = psi.decayProducts()[ix].at( 2212);
const Particles & pbar = psi.decayProducts()[ix].at(-2212);
double mminus = (pbar[0].momentum()+etap[0].momentum()).mass2();
double mplus = (pp [0].momentum()+etap[0].momentum()).mass2();
double mneut = (pp [0].momentum()+pbar[0].momentum()).mass2();
unsigned int iloc = psi.decaying()[ix].pid()==443 ? 1 : 0;
for(unsigned int ix=0;ix<4;ix+=3) {
_h[iloc][ix+2]->fill(sqrt(mneut ));
_h[iloc][ix+0]->fill(sqrt(mplus ));
_h[iloc][ix+1]->fill(sqrt(mminus));
}
_dalitz[iloc]->fill(mplus,mminus);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix) {
normalize(_dalitz[ix]);
for(unsigned int iy=0;iy<6;++iy) {
normalize(_h[ix][iy]);
}
}
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2][6];
Histo2DPtr _dalitz[2];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2019_I1709205);
}