// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief psi(2S) -> p pbar eta
class BESIII_2013_I1227512 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1227512);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(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<3;++ix)
book(_h[ix],1,1,1+ix);
book(_dalitz, "dalitz",50,2.,8.,50,2.,8.);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 2212,1}, {-2212,1}, { 221,1} };
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 Particle & eta = psi.decayProducts()[ix].at( 221 )[0];
const Particle & pp = psi.decayProducts()[ix].at( 2212)[0];
const Particle & pbar = psi.decayProducts()[ix].at(-2212)[0];
double mminus = (pbar.momentum()+eta.momentum()).mass2();
double mplus = (pp .momentum()+eta.momentum()).mass2();
_h[0]->fill(sqrt(mplus));
_h[1]->fill(sqrt(mminus));
_h[2]->fill((pp.momentum()+pbar.momentum()).mass());
_dalitz->fill(mplus,mminus);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_dalitz);
for(unsigned int ix=0;ix<3;++ix)
normalize(_h[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[3];
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2013_I1227512);
}