// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D0 -> K_S0 K+ K-
class BESIII_2020_I1799437 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1799437);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==421);
declare(ufs, "UFS");
DecayedParticles D0(ufs);
D0.addStable(PID::PI0);
D0.addStable(PID::K0S);
D0.addStable(PID::ETA);
D0.addStable(PID::ETAPRIME);
declare(D0, "D0");
// Histograms
book(_h_K0Km,1,1,3);
book(_h_K0Kp,1,1,2);
book(_h_KpKm,1,1,1);
book(_dalitz, "dalitz",50,0.9,1.9,50,0.9,1.9);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 321,1},{-321,1}, { 310,1}};
DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
// loop over particles
for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
if( ! D0.modeMatches(ix,3,mode) ) continue;
int sign = D0.decaying()[ix].pid()/421;
const Particles & K0 = D0.decayProducts()[ix].at(310);
const Particles & Kp = D0.decayProducts()[ix].at( sign*321);
const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
double mminus = (Km[0].momentum()+K0[0].momentum() ).mass2();
double mplus = (Kp[0].momentum()+K0[0].momentum() ).mass2();
double mKK = (Kp[0].momentum()+Km[0].momentum()).mass2();
_h_K0Kp->fill(mplus);
_h_K0Km->fill(mminus);
_h_KpKm->fill(mKK);
_dalitz->fill(mKK,mplus);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_K0Km);
normalize(_h_K0Kp);
normalize(_h_KpKm);
normalize(_dalitz);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_K0Km,_h_KpKm,_h_K0Kp;
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2020_I1799437);
}