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Rivet analyses reference
BELLE_2022_I2140379
Decay asymmetries in $\Lambda_c^+ \to \Sigma^+ \pi^0$, $\Sigma^+ \eta$, and $\Sigma^+ \eta^\prime$
Experiment: BELLE (KEKB)
Inspire ID: 2140379
Status: VALIDATED NOHEPDATA SINGLEWEIGHT
Authors:
References:
Beams: * *
Beam energies: ANY
Run details:
- Any process producing Lambda_c baryons
Decay asymmetries in $\Lambda_c^+ \to \Sigma^+ \pi^0$, $\Sigma^+ \eta$, and $\Sigma^+ \eta^\prime$
Source code:
BELLE_2022_I2140379.cc
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142 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Lambda_c -> Sigma+ pi0,eta,eta' decay asymmetries
class BELLE_2022_I2140379 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2140379);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS" );
// histograms
for(unsigned int ix=0;ix<3;++ix)
book(_h[ix],2,1,1+ix);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// loop over Lambda_c baryons
for( const Particle& Lambdac : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==4122)) {
int sign = Lambdac.pid()/4122;
if(Lambdac.children().size()!=2) continue;
Particle baryon1;
int imeson=-1;
if(Lambdac.children()[0].pid()==sign*3222 &&
Lambdac.children()[1].pid()==111) {
baryon1 = Lambdac.children()[0];
imeson=0;
}
else if(Lambdac.children()[1].pid()==sign*3222 &&
Lambdac.children()[0].pid()==111) {
baryon1 = Lambdac.children()[1];
imeson=0;
}
else if(Lambdac.children()[0].pid()==sign*3222 &&
Lambdac.children()[1].pid()==221) {
baryon1 = Lambdac.children()[0];
imeson=1;
}
else if(Lambdac.children()[1].pid()==sign*3222 &&
Lambdac.children()[0].pid()==221) {
baryon1 = Lambdac.children()[1];
imeson=1;
}
else if(Lambdac.children()[0].pid()==sign*3222 &&
Lambdac.children()[1].pid()==331) {
baryon1 = Lambdac.children()[0];
imeson=2;
}
else if(Lambdac.children()[1].pid()==sign*3222 &&
Lambdac.children()[0].pid()==331) {
baryon1 = Lambdac.children()[1];
imeson=2;
}
else
continue;
Particle baryon2;
if(baryon1.children()[0].pid()== sign*2212 &&
baryon1.children()[1].pid()== 111) {
baryon2 = baryon1.children()[0];
}
else if(baryon1.children()[1].pid()== sign*2212 &&
baryon1.children()[0].pid()== 111) {
baryon2 = baryon1.children()[1];
}
else
continue;
// first boost to the Lambdac rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(Lambdac.momentum().betaVec());
FourMomentum pbaryon1 = boost1.transform(baryon1.momentum());
FourMomentum pbaryon2 = boost1.transform(baryon2.momentum());
// to sigma+ 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);
_h[imeson]->fill(cTheta);
}
}
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() {
pair<double,double> aSigma(-.983,0.013);
for(unsigned int ix=0;ix<3;++ix) {
normalize(_h[ix]);
Scatter2DPtr _h_alpha1;
book(_h_alpha1,1,1+ix,1);
pair<double,double> alpha = calcAlpha(_h[ix]);
_h_alpha1->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
// divide out alpha Sigma
alpha.second = alpha.first/aSigma.first*
sqrt(sqr(alpha.second/alpha.first) + sqr(aSigma.second/aSigma.first));
alpha.first /= aSigma.first;
Scatter2DPtr _h_alpha2;
book(_h_alpha2,1,1+ix,2);
_h_alpha2->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
}
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}
};
RIVET_DECLARE_PLUGIN(BELLE_2022_I2140379);
}
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