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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief asymmetry in Omega-> Lambda K
class HyperCP_2005_I677384 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(HyperCP_2005_I677384);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS" );
// Book histograms
book(_h_cthetaP , "cthetaP" ,20,-1,1);
book(_h_cthetaM , "cthetaM" ,20,-1,1);
book(_h_cthetaAll, "cthetaAll",20,-1,1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// loop over Omega baryons
for(const Particle& Omega : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==3334)) {
int sign = Omega.pid()/3334;
if(Omega.children().size()!=2) continue;
Particle Lambda,kaon;
if(Omega.children()[0].pid()==sign*3122 &&
Omega.children()[1].pid()==-sign*321) {
Lambda = Omega.children()[0];
kaon = Omega.children()[1];
}
else if(Omega.children()[1].pid()==sign*3122 &&
Omega.children()[0].pid()==-sign*321) {
Lambda = Omega.children()[1];
kaon = Omega.children()[0];
}
else
continue;
if(Lambda.children().size()!=2) continue;
Particle proton,pion;
if(Lambda.children()[0].pid()==sign*2212 &&
Lambda.children()[1].pid()==-sign*211) {
proton = Lambda.children()[0];
pion = Lambda.children()[1];
}
else if(Lambda.children()[1].pid()==sign*2212 &&
Lambda.children()[0].pid()==-sign*211) {
proton = Lambda.children()[1];
pion = Lambda.children()[0];
}
else
continue;
// first boost to the Omega rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(Omega.momentum().betaVec());
FourMomentum pLambda = boost1.transform(Lambda.momentum());
FourMomentum pproton = boost1.transform(proton.momentum());
// to lambda rest frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pLambda.betaVec());
Vector3 axis = pLambda.p3().unit();
FourMomentum pp = boost2.transform(pproton);
// calculate angle
double cTheta = pp.p3().unit().dot(axis);
_h_cthetaAll->fill(cTheta,1.);
if(sign==1) {
_h_cthetaM->fill(cTheta,1.);
}
else {
_h_cthetaP->fill(cTheta,1.);
}
}
}
pair<double,double> calcAlpha(Histo1DPtr hist) {
if(hist->numEntries()==0.) return make_pair(0.,0.);
double sum1(0.),sum2(0.);
for (auto bin : hist->bins() ) {
double Oi = bin.area();
if(Oi==0.) continue;
double ai = 0.5*(bin.xMax()-bin.xMin());
double bi = 0.5*ai*(bin.xMax()+bin.xMin());
double Ei = bin.areaErr();
sum1 += sqr(bi/Ei);
sum2 += bi/sqr(Ei)*(Oi-ai);
}
return make_pair(sum2/sum1,sqrt(1./sum1));
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_cthetaP );
normalize(_h_cthetaM );
normalize(_h_cthetaAll);
// calculate the values of alpha
Scatter2DPtr _h_alphaP;
book(_h_alphaP,1,1,1);
pair<double,double> alpha = calcAlpha(_h_cthetaP);
_h_alphaP->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
Scatter2DPtr _h_alphaM;
book(_h_alphaM,1,1,2);
alpha = calcAlpha(_h_cthetaM);
_h_alphaM->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
Scatter2DPtr _h_alphaAll;
book(_h_alphaAll,1,1,3);
alpha = calcAlpha(_h_cthetaAll);
_h_alphaAll->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
}
//@}
/// @name Histograms
//@{
Histo1DPtr _h_cthetaP,_h_cthetaM,_h_cthetaAll;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(HyperCP_2005_I677384);
}
|