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106 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Xi* decay asymmetries
class BABAR_2008_I781294 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I781294);
/// @name Analysis methods
///@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS" );
// book histos
book(_h_ctheta,1,1,1);
book(_h_P0 ,2,1,1);
book(_h_P2 ,2,1,2);
book(_wgtSum,"/TMP/WSUM");
}
void findChildren(const Particle &p, int & sign,
unsigned int & nprod, Particles & Xi, Particles &pi,Particles &K) {
for(const Particle & child : p.children()) {
if(child.pid()==sign*3312) {
Xi.push_back(child);
++nprod;
}
else if(child.pid()==211) {
pi.push_back(child);
++nprod;
}
else if(child.pid()==321) {
K.push_back(child);
++nprod;
}
else if(child.children().empty()) {
++nprod;
}
else {
findChildren(child,sign,nprod,Xi,pi,K);
}
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// loop over Lambda_c
for(const Particle& baryon : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==4122)) {
int sign = baryon.pid()/baryon.abspid();
Particles Xi,pi,K;
unsigned int nprod(0);
findChildren(baryon,sign,nprod,Xi,pi,K);
// check Lambda_c -> Xi- pi+ K+ decya mode
if(nprod!=3||Xi.size()!=1||pi.size()!=1||K.size()!=1) continue;
// first boost to the Lambda_c rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(baryon.momentum().betaVec());
FourMomentum pbaryon1 = Xi[0].momentum()+pi[0].momentum();
pbaryon1 = boost1.transform(pbaryon1);
FourMomentum pbaryon2 = boost1.transform(Xi[0].momentum());
// to Xi* frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pbaryon1.betaVec());
Vector3 axis = pbaryon1.p3().unit();
FourMomentum pp = boost2.transform(pbaryon2);
// calculate angle
double cTheta = pp.p3().unit().dot(axis);
double mass = pbaryon1.mass();
if(mass>1.5 && mass< 1.65)
_h_ctheta->fill(cTheta);
_h_P0->fill(mass);
_h_P2->fill(mass,0.5*(3.*sqr(cTheta)-1.));
_wgtSum->fill();
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_ctheta);
normalize(_h_P0,1.,false);
normalize(_h_P2,1.,false);
}
///@}
/// @name Histograms
///@{
Histo1DPtr _h_ctheta, _h_P0,_h_P2;
CounterPtr _wgtSum;
///@}
};
RIVET_DECLARE_PLUGIN(BABAR_2008_I781294);
}
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