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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief tau -> pi-pi0 nu_tau
class CLEO_1999_I508944 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_1999_I508944);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
declare(UnstableParticles(), "UFS");
book(_hist_pipi, 1, 1, 1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Find the taus
Particles taus;
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p : ufs.particles()) {
if (p.abspid() != PID::TAU) continue;
Particles pip, pim, pi0;
unsigned int nstable = 0;
// get the boost to the rest frame
// find the decay products we want
findDecayProducts(p, nstable, pip, pim, pi0);
if (p.pid() < 0) {
swap(pip, pim);
}
if (nstable != 3) continue;
// pipi
if (pim.size() == 1 && pi0.size() == 1)
_hist_pipi->fill((pi0[0].momentum()+pim[0].momentum()).mass());
}
}
void findDecayProducts(const Particle & mother,
unsigned int & nstable,
Particles& pip, Particles& pim,
Particles& pi0) {
for(const Particle & p : mother.children()) {
long id = p.pid();
if (id == PID::PI0 ) {
pi0.push_back(p);
++nstable;
}
else if (id == PID::PIPLUS) {
pip.push_back(p);
++nstable;
}
else if (id == PID::PIMINUS) {
pim.push_back(p);
++nstable;
}
else if (id == PID::K0S || id == PID::KPLUS ||
id == PID::KMINUS) {
++nstable;
}
else if ( !p.children().empty() ) {
findDecayProducts(p, nstable, pip, pim, pi0);
}
else
++nstable;
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_hist_pipi);
}
//@}
/// @name Histograms
//@{
Histo1DPtr _hist_pipi;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(CLEO_1999_I508944);
}
|