// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief B0 > KS0 pi+ pi-
class BABAR_2009_I821188 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I821188);
/// @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(PID::K0S);
declare(B0, "B0");
// histograms
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
book(_h[ix][iy],1+ix,1,1+iy);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode = { { 310,1}, { 211,1}, {-211,1}};
DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
// loop over particles
for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
if (!B0.modeMatches(ix,3,mode)) continue;
int sign = B0.decaying()[ix].pid()>0 ? 1 : -1;
// boost to B rest frame
LorentzTransform boost =
LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix]. momentum().betaVec());
// momenta
FourMomentum pip = boost.transform(B0.decayProducts()[ix].at( 211*sign)[0].momentum());
FourMomentum pim = boost.transform(B0.decayProducts()[ix].at(-211*sign)[0].momentum());
FourMomentum K0 = boost.transform(B0.decayProducts()[ix].at( 310 )[0].momentum());
// pi+pi- resonance
FourMomentum ppipi = pim+pip;
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
double cTheta = boost2.transform(pim).p3().unit().dot(K0.p3().unit());
if(cTheta>0.) _h[0][0]->fill(ppipi.mass());
else _h[0][1]->fill(ppipi.mass());
// K pi- resonance
FourMomentum pKpim = K0+pim;
boost2 = LorentzTransform::mkFrameTransformFromBeta(pKpim.betaVec());
cTheta = boost2.transform(K0).p3().unit().dot(pip.p3().unit());
if(cTheta>0.) _h[1][0]->fill(pKpim.mass());
else _h[1][1]->fill(pKpim.mass());
// K pi+ resonance
FourMomentum pKpip = K0+pip;
boost2 = LorentzTransform::mkFrameTransformFromBeta(pKpip.betaVec());
cTheta = boost2.transform(pip).p3().unit().dot(pim.p3().unit());
if(cTheta>0.) _h[1][0]->fill(pKpip.mass());
else _h[1][1]->fill(pKpip.mass());
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
normalize(_h[ix][iy],1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[2][2];
/// @}
};
RIVET_DECLARE_PLUGIN(BABAR_2009_I821188);
}