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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief b-baryon polarization
class DELPHI_2000_I513614 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_2000_I513614);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// Book histograms
book(_h_El, "El", 45,0.,45.0);
book(_h_Ev, "Ev", 45,0.,45.0);
}
void findDecayProducts(Particle p, Particles & lep, Particles & nu) {
for(const Particle & child : p.children()) {
if(PID::isHadron(child.pid())) continue;
if(child.abspid()==11 or child.abspid()==13)
lep.push_back(child);
else if(child.abspid()==12 or child.abspid()==14)
nu.push_back(child);
else if(child.abspid()!=15)
findDecayProducts(child,lep,nu);
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
// loop over weakly decaying b-baryons
for (const Particle& p : ufs.particles(Cuts::abspid==5122 || Cuts::abspid==5132 ||
Cuts::abspid==5232 || Cuts::abspid==5332)) {
Particles lep,nu;
findDecayProducts(p,lep,nu);
if(lep.size()!=1 || nu.size()!=1) continue;
_h_El ->fill(lep[0].momentum().t());
_h_Ev ->fill(nu [0].momentum().t());
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_El );
normalize(_h_Ev );
if(_h_El->effNumEntries()!=0. and _h_Ev->effNumEntries()!=0.) {
double Ev = _h_Ev->xMean();
double El = _h_El->xMean();
double dEv = _h_Ev->xStdErr();
double dEl = _h_El->xStdErr();
double ratio = El/Ev;
double dr = (Ev*dEl-El*dEv)/sqr(Ev);
double rho = 0.091;
double P = (7. + rho*(30. - 40.*ratio) + 4.*(2.-3.*ratio)*ratio)/sqr(1.+2.*ratio);
double dP = (20.*(-1. + 4.*rho*(-2. + ratio) - 2.*ratio))/pow(1. + 2.*ratio,3)*dr;
Scatter2DPtr h_pol;
book(h_pol, 1,1,1);
h_pol->addPoint(91.2, P, make_pair(0.5,0.5),make_pair(dP,dP) );
}
}
//@}
/// @name Histograms
//@{
Histo1DPtr _h_El, _h_Ev;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(DELPHI_2000_I513614);
}
|