// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief Bs0 -> pi+ pi- J/psi
class BELLE_2011_I889524 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2011_I889524);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==531);
declare(ufs, "UFS");
DecayedParticles BS0(ufs);
BS0.addStable( 443);
declare(BS0, "BS0");
// histograms
book(_h_mass,1,1,1);
for(unsigned int ix=0;ix<2;++ix)
book(_h_cTheta[ix],2,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 211,1}, {-211,1}, { 443,1}};
DecayedParticles BS0 = apply<DecayedParticles>(event, "BS0");
for(unsigned int ix=0;ix<BS0.decaying().size();++ix) {
if (!BS0.modeMatches(ix,3,mode)) continue;
const Particle & pip = BS0.decayProducts()[ix].at( 211)[0];
const Particle & pim = BS0.decayProducts()[ix].at(-211)[0];
const Particle & JPsi = BS0.decayProducts()[ix].at( 443)[0];
double mpipi = (pip.momentum()+pim.momentum()).mass();
_h_mass->fill(mpipi);
// helicity angle find J.psi leptonic children
if(JPsi.children().size()!=2) continue;
if(JPsi.children()[0].pid()!=-JPsi.children()[1].pid()) continue;
if(JPsi.children()[0].abspid()!=PID::EMINUS &&
JPsi.children()[0].abspid()!=PID::MUON) continue;
Particle lm = JPsi.children()[0];
Particle lp = JPsi.children()[1];
if(lm.pid()<0) swap(lm,lp);
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(BS0.decaying()[ix].momentum().betaVec());
FourMomentum ppsi = boost1.transform(JPsi.momentum());
Vector3 axis1 = ppsi.p3().unit();
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppsi.betaVec());
FourMomentum plp = boost2.transform(boost1.transform(lp.momentum()));
double cTheta = plp.p3().unit().dot(axis1);
if (mpipi>0.8 && mpipi<1.16) _h_cTheta[0]->fill(cTheta);
else if(mpipi>1.3 && mpipi<1.5) _h_cTheta[1]->fill(cTheta);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_mass,1.,false);
for(unsigned int ix=0;ix<2;++ix)
normalize(_h_cTheta[ix],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_mass,_h_cTheta[2];
/// @}
};
RIVET_DECLARE_PLUGIN(BELLE_2011_I889524);
}