// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D0 -> K- pi+ pi+ pi-
class BESIII_2017_I1511280 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1511280);
/// @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<8;++ix)
book(_h[ix],1,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// define the decay mode
static const map<PdgId,unsigned int> & mode = { {-321,1},{ 211,2}, {-211,1}};
static const map<PdgId,unsigned int> & modeCC = { { 321,1},{-211,2}, { 211,1}};
DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
// loop over particles
for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
int sign = 1;
if (D0.decaying()[ix].pid()>0 && D0.modeMatches(ix,4,mode)) {
sign=1;
}
else if (D0.decaying()[ix].pid()<0 && D0.modeMatches(ix,4,modeCC)) {
sign=-1;
}
else
continue;
const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
const Particles & pip= D0.decayProducts()[ix].at( sign*211);
const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
// first pip gives higher pi+pi- mass
double mpipi[2] = {(pip[0].momentum()+pim[0].momentum()).mass(),
(pip[1].momentum()+pim[0].momentum()).mass()};
unsigned int i1= mpipi[0]>mpipi[1] ? 0 : 1;
unsigned int i2= i1==0 ? 1 : 0;
_h[0]->fill((Km [0].momentum()+pip[i1].momentum()).mass());
_h[1]->fill((Km [0].momentum()+pip[i2].momentum()).mass());
_h[2]->fill(sqr(mpipi[i1]));
_h[3]->fill(sqr(mpipi[i2]));
_h[4]->fill((Km [0].momentum()+pim[0].momentum()+pip[i1].momentum()).mass());
_h[5]->fill((Km [0].momentum()+pim[0].momentum()+pip[i2].momentum()).mass());
_h[6]->fill((pim[0].momentum()+pip[i1].momentum()+pip[i2].momentum()).mass());
_h[7]->fill((Km [0].momentum()+pip[i1].momentum()+pip[i2].momentum()).mass());
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<8;++ix)
normalize(_h[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[8];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2017_I1511280);
}