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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include <sstream>
namespace Rivet {
/// @brief asymmetrics in Xi0 decays
class NA48_2010_I868871 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(NA48_2010_I868871);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS" );
// Book histograms
book(_h_ctheta_pi0 , "ctheta_pi0" , 20,-1,1);
book(_h_ctheta_gamma, "ctheta_gamma", 20,-1,1);
double step=0.1;
double xmin=-1.;
for(unsigned int ix=0;ix<20;++ix) {
Histo1DPtr temp;
std::ostringstream title;
title << "ctheta_Sigma_" << ix;
book(temp,title.str(), 20,-1,1);
_h_ctheta_Sigma.add(xmin, xmin+step, temp);
xmin+=step;
}
_nSigma=0.;
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// loop over Omega baryons
for(const Particle& Xi : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==3322)) {
int sign = Xi.pid()/3322;
if(Xi.children().size()!=2) continue;
Particle baryon1,meson1;
unsigned int mode(0);
if(Xi.children()[0].pid()==sign*3122 &&
Xi.children()[1].pid()==111) {
baryon1 = Xi.children()[0];
meson1 = Xi.children()[1];
mode=1;
}
else if(Xi.children()[1].pid()==sign*3122 &&
Xi.children()[0].pid()==111) {
baryon1 = Xi.children()[1];
meson1 = Xi.children()[0];
mode=1;
}
else if(Xi.children()[0].pid()==sign*3122 &&
Xi.children()[1].pid()==22) {
baryon1 = Xi.children()[0];
meson1 = Xi.children()[1];
mode=2;
}
else if(Xi.children()[1].pid()==sign*3122 &&
Xi.children()[0].pid()==22) {
baryon1 = Xi.children()[1];
meson1 = Xi.children()[0];
mode=2;
}
else if(Xi.children()[0].pid()==sign*3212 &&
Xi.children()[1].pid()==22) {
baryon1 = Xi.children()[0];
meson1 = Xi.children()[1];
mode=3;
}
else if(Xi.children()[1].pid()==sign*3212 &&
Xi.children()[0].pid()==22) {
baryon1 = Xi.children()[1];
meson1 = Xi.children()[0];
mode=3;
}
else
continue;
if(baryon1.children().size()!=2) continue;
Particle baryon2,meson2,baryon3,meson3;
if(mode==1 || mode ==2) {
if(baryon1.children()[0].pid()== sign*2212 &&
baryon1.children()[1].pid()==-sign*211) {
baryon2 = baryon1.children()[0];
meson2 = baryon1.children()[1];
}
else if(baryon1.children()[1].pid()== sign*2212 &&
baryon1.children()[0].pid()==-sign*211) {
baryon2 = baryon1.children()[1];
meson2 = baryon1.children()[0];
}
else
continue;
}
else if(mode==3) {
if(baryon1.children()[0].pid()== sign*3122 &&
baryon1.children()[1].pid()== 22) {
baryon2 = baryon1.children()[0];
meson2 = baryon1.children()[1];
}
else if(baryon1.children()[1].pid()== sign*3122 &&
baryon1.children()[0].pid()== 22) {
baryon2 = baryon1.children()[1];
meson2 = baryon1.children()[0];
}
else
continue;
if(baryon2.children()[0].pid()== sign*2212 &&
baryon2.children()[1].pid()==-sign*211) {
baryon3 = baryon2.children()[0];
meson3 = baryon2.children()[1];
}
else if(baryon2.children()[1].pid()== sign*2212 &&
baryon2.children()[0].pid()==-sign*211) {
baryon3 = baryon2.children()[1];
meson3 = baryon2.children()[0];
}
else
continue;
}
// first boost to the Xi rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(Xi.momentum().betaVec());
FourMomentum pbaryon1 = boost1.transform(baryon1.momentum());
FourMomentum pbaryon2 = boost1.transform(baryon2.momentum());
// to lambda rest 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);
if(mode==1) {
_h_ctheta_pi0->fill(cTheta,1.);
}
else if(mode==2) {
_h_ctheta_gamma->fill(cTheta,1.);
}
else if(mode==3) {
FourMomentum pbaryon3 = boost1.transform(baryon3.momentum());
FourMomentum pp2 = boost2.transform(pbaryon3);
Vector3 axis2 = pp.p3().unit();
double cTheta2 = pp2.p3().unit().dot(axis2);
_h_ctheta_Sigma.fill(cTheta,cTheta2,1.);
_nSigma += 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));
}
pair<double,double> calcAlpha(BinnedHistogram hist) {
double sum1(0.),sum2(0.);
double step=0.1;
double xmin=-1.;
for(unsigned int ix=0;ix<20;++ix) {
double xsum=2.*xmin+step;
Histo1DPtr h2 = hist.histo(xmin+0.5*step);
for (auto bin : h2->bins() ) {
double Oi = bin.area();
if(Oi==0.) continue;
double ai = 0.25*(bin.xMax()-bin.xMin())*step;
double bi = 0.25*ai*(bin.xMax()+bin.xMin())*xsum;
double Ei = bin.areaErr();
sum1 += sqr(bi/Ei);
sum2 += bi/sqr(Ei)*(Oi-ai);
}
xmin+=step;
}
return make_pair(sum2/sum1,sqrt(1./sum1));
}
/// Normalise histograms etc., after the run
void finalize() {
// Xi0 -> Lambda0 pi0
normalize(_h_ctheta_pi0);
Scatter2DPtr _h_alpha_pi0;
book(_h_alpha_pi0,1,1,1);
pair<double,double> alpha = calcAlpha(_h_ctheta_pi0);
_h_alpha_pi0->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
// Xi0 -> Lambda gamma (N.B. sign due defns)
normalize(_h_ctheta_gamma);
Scatter2DPtr _h_alpha_gamma;
book(_h_alpha_gamma,2,1,1);
alpha = calcAlpha(_h_ctheta_gamma);
_h_alpha_gamma->addPoint(0.5,-alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
// Xi0 -> Sigma gamma
_h_ctheta_Sigma.scale(1./_nSigma,this);
Scatter2DPtr _h_alpha_Sigma;
book(_h_alpha_Sigma,3,1,1);
alpha = calcAlpha(_h_ctheta_Sigma);
_h_alpha_Sigma->addPoint(0.5,alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
}
//@}
/// @name Histograms
//@{
Histo1DPtr _h_ctheta_pi0,_h_ctheta_gamma;
BinnedHistogram _h_ctheta_Sigma;
double _nSigma;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(NA48_2010_I868871);
}
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