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122 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief D0 -> omega phi
class BESIII_2022_I1900094 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I1900094);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(Cuts::abspid==PID::D0), "UFS");
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1,1,1+ix);
}
void findDecayProducts(const Particle & mother, unsigned int & nstable,
Particles & pip , Particles & pim , Particles & pi0) {
for(const Particle & p : mother.children()) {
int id = p.pid();
if ( id == PID::KPLUS || id == PID::KMINUS || id == PID::K0S || id == PID::K0L ) {
++nstable;
}
else if (id == PID::PIPLUS) {
pip.push_back(p);
++nstable;
}
else if (id == PID::PIMINUS) {
pim.push_back(p);
++nstable;
}
else if (id == PID::PI0) {
pi0.push_back(p);
++nstable;
}
else if ( !p.children().empty() ) {
findDecayProducts(p, nstable, pip, pim, pi0);
}
else
++nstable;
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
for(const Particle & D0 : apply<UnstableParticles>(event, "UFS").particles()) {
Particle omega,phi;
if(D0.children()[0].pid()==PID::OMEGA && D0.children()[1].pid()==PID::PHI) {
omega = D0.children()[0];
phi = D0.children()[1];
}
else if(D0.children()[1].pid()==PID::OMEGA && D0.children()[0].pid()==PID::PHI) {
omega = D0.children()[1];
phi = D0.children()[0];
}
else
continue;
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(D0.momentum().betaVec());
// first the phi
if(phi.children().size()==2 &&
phi.children()[0].abspid()==PID::KPLUS &&
phi.children()[1].abspid()==PID::KPLUS ) {
// first boost all relevant momenta to D0 rest frame
FourMomentum pD0 = boost.transform(D0.momentum());
FourMomentum pphi = boost.transform(phi.momentum());
FourMomentum pK = boost.transform(phi.children()[0].momentum());
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pphi.betaVec());
Vector3 axis1 = boost2.transform(pD0).p3().unit();
Vector3 axis2 = boost2.transform(pK ).p3().unit();
_h[1]->fill(abs(axis1.dot(axis2)));
}
// then the omega
unsigned int nstable(0);
Particles pip, pim, pi0;
findDecayProducts(omega, nstable, pip, pim, pi0);
if(nstable==3 && pip.size()==1 && pip.size()==1 && pi0.size()==1) {
FourMomentum pD0 = boost.transform(D0.momentum());
FourMomentum pomega = boost.transform(omega.momentum() );
FourMomentum ppip = boost.transform(pip[0].momentum());
FourMomentum ppim = boost.transform(pim[0].momentum());
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pomega.betaVec());
Vector3 axis = boost2.transform(pD0).p3().unit();
Vector3 pp = boost2.transform(ppip).p3();
Vector3 pm = boost2.transform(ppim).p3();
Vector3 axis2 = pp.cross(pm).unit();
_h[0]->fill(abs(axis.dot(axis2)));
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix) normalize(_h[ix]);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2022_I1900094);
}
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