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103 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief J/psi -> eta(1405)
class BESIII_2012_I1084539 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2012_I1084539);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==443);
declare(ufs, "UFS");
declare(Beam(), "Beams");
// histos
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// get the axis, direction of incoming electron
const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
Vector3 axis;
if(beams.first.pid()>0)
axis = beams.first .momentum().p3().unit();
else
axis = beams.second.momentum().p3().unit();
Particles psi = apply<UnstableParticles>(event,"UFS").particles();
if(psi.size()!=1 || psi[0].children().size()!=2) vetoEvent;
Particle gamma,eta;
if(psi[0].children()[0].pid()==PID::GAMMA &&
psi[0].children()[1].pid()==9020221) {
gamma = psi[0].children()[0];
eta = psi[0].children()[1];
}
else if(psi[0].children()[1].pid()==PID::GAMMA &&
psi[0].children()[0].pid()==9020221) {
gamma = psi[0].children()[1];
eta = psi[0].children()[0];
}
else
vetoEvent;
if(eta.children().size()!=2) vetoEvent;
// eta(1405) -> f0(980) pi0
Particle f0,pi0;
if(eta.children()[0].pid()==PID::PI0 &&
eta.children()[1].pid()==9010221) {
pi0 = eta.children()[0];
f0 = eta.children()[1];
}
else if(eta.children()[1].pid()==PID::PI0 &&
eta.children()[0].pid()==9010221) {
pi0 = eta.children()[1];
f0 = eta.children()[0];
}
else
vetoEvent;
double cTheta = axis.dot(gamma.p3().unit());
_h[1]->fill(cTheta);
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(psi[0].momentum().betaVec());
FourMomentum pGamma = boost1.transform(gamma.momentum());
Vector3 axis1 = pGamma.p3().unit();
FourMomentum pEta = boost1.transform(eta.momentum());
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pEta.betaVec());
FourMomentum pf0 = boost2.transform(boost1.transform(f0.momentum()));
_h[0]->fill(pf0.p3().unit().dot(axis1));
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix)
normalize(_h[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2012_I1084539);
}
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