// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D_s+ -> pi+ pi0 pi0
class BESIII_2021_I1929365 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1929365);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==431);
declare(ufs, "UFS");
DecayedParticles DS(ufs);
DS.addStable(PID::PI0);
DS.addStable(PID::K0S);
declare(DS,"DS");
// histos
book(_h_pi0pi0,1,1,1);
book(_h_pippi0,1,1,2);
book(_dalitz, "dalitz",50,0.,3.5,50,0.,3.5);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 211,1},{ 111,2}};
static const map<PdgId,unsigned int> & modeCC = { {-211,1},{ 111,2}};
DecayedParticles DS = apply<DecayedParticles>(event, "DS");
// loop over particles
for(unsigned int ix=0;ix<DS.decaying().size();++ix) {
int sign = 1;
if (DS.decaying()[ix].pid()>0 && DS.modeMatches(ix,3,mode)) {
sign=1;
}
else if (DS.decaying()[ix].pid()<0 && DS.modeMatches(ix,3,modeCC)) {
sign=-1;
}
else
continue;
const Particles & pi0 = DS.decayProducts()[ix].at( 111);
const Particle & pip = DS.decayProducts()[ix].at( sign*211)[0];
double mp1 = (pip .momentum() +pi0[0].momentum()).mass2();
double mp2 = (pip .momentum() +pi0[1].momentum()).mass2();
double m0 = (pi0[0].momentum() +pi0[1].momentum()).mass();
_dalitz ->fill(mp1,mp2);
_dalitz ->fill(mp2,mp1);
// K_S0 veto
if(m0>0.458 && m0<0.520) continue;
_h_pippi0->fill(sqrt(mp1));
_h_pippi0->fill(sqrt(mp2));
_h_pi0pi0->fill(m0 );
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_pi0pi0);
normalize(_h_pippi0);
normalize(_dalitz );
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_pi0pi0,_h_pippi0;
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2021_I1929365);
}