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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief D*+/- in Upsilon(1S) decays
class BABAR_2009_I836615 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I836615);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// book the histogram
book(_hist,1,1,1);
}
/// Recursively walk the decay tree to find decay products of @a p
void findDecayProducts(Particle mother, Particles& unstable) {
for(const Particle & p: mother.children()) {
const int id = abs(p.pid());
if(id == 413) {
unstable.push_back(p);
}
if(!p.children().empty())
findDecayProducts(p, unstable);
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// maximum momentum of D* calculated using PDG 2008 masses (as in paper)
static const double Pmax = 4.28172;
// Loop over the upsilons
// Find the Upsilons among the unstables
for(const Particle & ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==553)) {
// boost to rest frame
LorentzTransform boost;
if (ups.p3().mod() > 1*MeV)
boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
// find D*
Particles unstable;
findDecayProducts(ups,unstable);
// loop over D*
for(const Particle& p : unstable) {
const FourMomentum p2 = boost.transform(p.momentum());
const double xP = p2.p3().mod()/Pmax;
_hist->fill(xP);
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_hist);
}
//@}
/// @name Histograms
//@{
Histo1DPtr _hist;
//@}
};
RIVET_DECLARE_PLUGIN(BABAR_2009_I836615);
}
|