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106 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief B0 -> phi K*
class BELLE_2013_I1247059 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1247059);
/// @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");
DecayedParticles B0(ufs);
B0.addStable(333);
declare(B0, "B0");
// histograms
for(unsigned int ix=0;ix<4;++ix)
book(_h[ix],1,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 321,1},{-211,1}, { 333,1}};
static const map<PdgId,unsigned int> & modeCC = { {-321,1},{ 211,1}, { 333,1}};
DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
// loop over particles
for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
int sign = 1;
if (B0.decaying()[ix].pid()>0 && B0.modeMatches(ix,3,mode)) {
sign=1;
}
else if (B0.decaying()[ix].pid()<0 && B0.modeMatches(ix,3,modeCC)) {
sign=-1;
}
else
continue;
const Particle & Kp = B0.decayProducts()[ix].at( 321*sign)[0];
const Particle & pim = B0.decayProducts()[ix].at(-211*sign)[0];
const Particle & phi = B0.decayProducts()[ix].at( 333 )[0];
if(phi.children().size()!=2 || phi.children()[0].pid()!=-phi.children()[1].pid() ||
phi.children()[0].abspid()!=321) continue;
Particle Kp1 = phi.children()[0];
Particle Km1 = phi.children()[1];
if(Kp1.pid()<0) swap(Kp1,Km1);
// B0 frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].momentum().betaVec());
FourMomentum pKstar = boost1.transform(Kp.momentum()+pim.momentum());
FourMomentum pPhi = boost1.transform(phi.momentum());
// stuff in K* frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
FourMomentum pKp = boost2.transform(boost1.transform(Kp.momentum()));
Vector3 axis1 = pKstar.p3().unit();
double cTheta1 = axis1.dot(pKp.p3().unit());
if(cTheta1>0.75) continue;
Vector3 trans1 = pKp.p3() - cTheta1*pKp.p3().mod()*axis1;
// stuff in phi frame
LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
Vector3 axis2 = pPhi.p3().unit();
double cTheta2 = axis2.dot(pKp1.p3().unit());
Vector3 trans2 = pKp1.p3() - cTheta2*pKp1.p3().mod()*axis2;
// angle between planes
double chi = atan2(trans1.cross(trans2).dot(axis1),trans1.dot(trans2));
// fill histos
_h[0]->fill(pKstar.mass());
_h[1]->fill(cTheta1);
_h[2]->fill(cTheta2);
_h[3]->fill(chi);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<4;++ix)
normalize(_h[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[4];
/// @}
};
RIVET_DECLARE_PLUGIN(BELLE_2013_I1247059);
}
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