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106 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D0 -> Kbar0 pi- e+ nu_e
class BESIII_2018_I1705754 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1705754);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::pid==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");
// Book histograms
for(unsigned int ix=0;ix<5;++ix)
book(_h[ix],1,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode1 = { { 310,1}, {-211,1}, {-11,1}, { 12,1}};
static const map<PdgId,unsigned int> & mode2 = { { 130,1}, {-211,1}, {-11,1}, { 12,1}};
static const map<PdgId,unsigned int> & mode3 = { {-311,1}, {-211,1}, {-11,1}, { 12,1}};
DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
// loop over particles
for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
Particle K0;
if (D0.modeMatches(ix,4,mode1)) K0=D0.decayProducts()[ix].at( 310)[0];
else if(D0.modeMatches(ix,4,mode2)) K0=D0.decayProducts()[ix].at( 130)[0];
else if(D0.modeMatches(ix,4,mode3)) K0=D0.decayProducts()[ix].at(-311)[0];
else continue;
const Particle & pim= D0.decayProducts()[ix].at(-211)[0];
const Particle & ep = D0.decayProducts()[ix].at(-11)[0];
const Particle & nue= D0.decayProducts()[ix].at( 12)[0];
FourMomentum pKstar = K0.momentum()+pim.momentum();
_h[0]->fill(pKstar.mass());
FourMomentum qq = D0.decaying()[ix].momentum()-pKstar;
_h[1]->fill(qq.mass2());
// boost momenta to D0 rest frame
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(D0.decaying()[ix].momentum().betaVec());
FourMomentum pKS = boost.transform(pKstar);
Matrix3 ptoz(-pKS.p3().unit(), Vector3(0,0,1));
boost.preMult(ptoz);
// the momenta in frane to W along z
FourMomentum pD = boost.transform(D0.decaying()[ix].momentum());
FourMomentum pK = boost.transform(K0 .momentum());
FourMomentum ppi = boost.transform(pim.momentum());
FourMomentum pe = boost.transform(ep .momentum());
FourMomentum pnu = boost.transform(nue.momentum());
pKstar = pK+ppi;
qq = pD-pKstar;
LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
Vector3 axisK = boostK.transform(pK).p3().unit();
_h[3]->fill(axisK.dot(pKstar.p3().unit()));
LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta( qq.betaVec());
Vector3 axisE = boostW.transform(pe).p3().unit();
_h[2]->fill(axisE.dot(qq.p3().unit()));
axisK.setZ(0.);
axisE.setZ(0.);
double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
_h[4]->fill(chi);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<5;++ix)
normalize(_h[ix]);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[5];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2018_I1705754);
}
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