Rivet analyses

title: BABAR_2009_I836615

Spectrum for $D^{*\pm}$ in $\Upsilon(1S)$ decays

Experiment: BABAR (PEP-II)

Inspire ID: 836615

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D81 (2010) 011102

Beams: * *

Beam energies: ANY

Run details: - Any process producing Upsilon(1S) mesons, original e+e-

Spectrum for $D^{*\pm}$ in $\Upsilon(1S)$ decays measured by Babar

Source code:BABAR_2009_I836615.cc

```c++ // -- 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);

} ```