// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief J/psi -> p pbar pi0
class BESII_2009_I819937 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2009_I819937);
/// @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)
book(_h[ix],1,1,1+ix);
book(_dalitz, "dalitz",50,1.,5.,50,1.,5.);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 2212,1}, {-2212,1}, { 111,1} };
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 & pi0 = psi.decayProducts()[ix].at( 111);
const Particles & pp = psi.decayProducts()[ix].at( 2212);
const Particles & pbar = psi.decayProducts()[ix].at(-2212);
double mminus = (pbar[0].momentum()+pi0 [0].momentum()).mass2();
double mplus = (pp [0].momentum()+pi0 [0].momentum()).mass2();
_h[0]->fill(sqrt(mplus ));
_h[1]->fill(sqrt(mminus));
_dalitz->fill(mplus,mminus);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_dalitz);
for(unsigned int ix=0;ix<2;++ix)
normalize(_h[ix]);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2];
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESII_2009_I819937);
}