// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D0 -> KS0, KL0 pi+ pi-
class BESIII_2022_I2615968 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2615968);
/// @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
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<3;++iy)
book(_h[ix][iy],1+ix,1,1+iy);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// // define the decay mode
static const map<PdgId,unsigned int> & mode1 = { { 310,1}, { 211,1},{-211,1}};
static const map<PdgId,unsigned int> & mode2 = { { 130,1}, { 211,1},{-211,1}};
DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
// loop over particles
for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
int sign = D0.decaying()[ix].pid()/421;
int imode = 0;
// KS0 pi+pi-
if (D0.modeMatches(ix,3,mode1) ) imode=0;
else if (D0.modeMatches(ix,3,mode2) ) imode=1;
else continue;
const Particle & pip= D0.decayProducts()[ix].at( sign*211)[0];
const Particle & pim= D0.decayProducts()[ix].at(-sign*211)[0];
const Particle & K0 = D0.decayProducts()[ix].at( imode==0 ? 310 : 130)[0];
double mminus = (pim.momentum()+K0.momentum() ).mass2();
double mplus = (pip.momentum()+K0.momentum() ).mass2();
double mpipi = (pip.momentum()+pim.momentum()).mass2();
_h[imode][0]->fill(mplus );
_h[imode][1]->fill(mminus);
_h[imode][2]->fill(mpipi );
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<3;++iy)
normalize(_h[ix][iy],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2][3];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2022_I2615968);
}