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103 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief B0 -> D*+ D*-
class BELLE_2012_I1123656 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2012_I1123656);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
declare(ufs, "UFS");
// histograms
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) {
Particles B0 = apply<UnstableParticles>(event, "UFS").particles();
for(const Particle & p : B0) {
if(p.children().size()!=2) continue;
if(p.children()[0].pid()!=-p.children()[1].pid()) continue;
if(p.children()[0].abspid()!=413) continue;
Particle Dp = p.children()[0];
Particle Dm = p.children()[1];
if (p.pid()>0 && Dp.pid()<0) swap(Dp,Dm);
else if(p.pid()<0 && Dp.pid()>0) swap(Dp,Dm);
// find children of the D mesons
Particle pip,pim;
if(Dp.children().size()!=2) continue;
if(Dp.children()[0].abspid()==PID::PIPLUS &&
Dp.children()[1].abspid()==PID::D0)
pip = Dp.children()[0];
else if (Dp.children()[1].abspid()==PID::PIPLUS &&
Dp.children()[0].abspid()==PID::D0)
pip = Dp.children()[1];
else
continue;
if(Dm.children().size()!=2) continue;
if(Dm.children()[0].abspid()==PID::PIPLUS &&
Dm.children()[1].abspid()==PID::D0) {
pim = Dm.children()[0];
}
else if (Dm.children()[1].abspid()==PID::PIPLUS &&
Dm.children()[0].abspid()==PID::D0) {
pim = Dm.children()[1];
}
else
continue;
// boost to rest frame
LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
FourMomentum pDstarPlus = boostB.transform(Dp.momentum());
FourMomentum pDstarMinus = boostB.transform(Dm.momentum());
LorentzTransform boostDp = LorentzTransform::mkFrameTransformFromBeta(pDstarPlus .betaVec());
FourMomentum ppip = boostDp.transform(boostB.transform(pip.momentum()));
LorentzTransform boostDm = LorentzTransform::mkFrameTransformFromBeta(pDstarMinus.betaVec());
FourMomentum ppim = boostDm.transform(boostB.transform(pim.momentum()));
Vector3 axisX = pDstarPlus.p3().unit();
// ctheta1
_h[1]->fill(axisX.dot(ppim.p3().unit()));
// y and z axis
ppim = boostDp.transform(boostB.transform(pim.momentum()));
Vector3 axisZ = axisX.cross(ppim.p3()).unit();
// cThetaTr
_h[0]->fill(axisZ.dot(ppip.p3().unit()));
}
}
/// 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(BELLE_2012_I1123656);
}
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