// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief chi_c1 -> eta pi+pi-
class BESIII_2017_I1490896 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1490896);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::pid==20443);
declare(ufs, "UFS");
DecayedParticles chi(ufs);
chi.addStable( PID::PI0);
chi.addStable( PID::K0S);
chi.addStable( PID::ETA);
declare(chi, "chi");
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1,1,ix+1);
book(_dalitz,"dalitz",50,0.,12.,50,0., 9.);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode1 = { { 221,1}, { 211,1}, {-211,1} };
DecayedParticles chi = apply<DecayedParticles>(event, "chi");
// loop over particles
for(unsigned int ix=0;ix<chi.decaying().size();++ix) {
if(chi.modeMatches(ix,3,mode1)) {
const Particle & eta = chi.decayProducts()[ix].at( 221)[0];
const Particle & pim = chi.decayProducts()[ix].at(-211)[0];
const Particle & pip = chi.decayProducts()[ix].at( 211)[0];
double m1 = (pip.momentum()+pim.momentum()).mass2();
double m2 = (eta.momentum()+pip.momentum()).mass2();
double m3 = (eta.momentum()+pim.momentum()).mass2();
_dalitz->fill(m2,m1);
_h[1]->fill(sqrt(m1));
_h[0]->fill(sqrt(m2));
_h[0]->fill(sqrt(m3));
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_dalitz);
for(unsigned int iy=0;iy<2;++iy)
normalize(_h[iy]);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2];
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2017_I1490896);
}