Rivet analyses

title: CLEOII_2002_I601701

Spectra of $\eta^\prime$ mesons in $\Upsilon(1S)$ decays

Experiment: CLEO-II (CESR)

Inspire ID: 601701

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D67 (2003) 052003

Beams: * *

Beam energies: ANY

Run details: - Any process producing Upslion 1S, original $e^+ e^-$

Measurement of the inclusive production of the $\eta^\prime$ mesons in $\Upsilon(1S)$ decays by the CLEO-II experiment. In principle this measurement is superseeded, however the newer result (CLEOIII_2006_I728679) did not include numerical values which were read from the plots and therefore we keep this measurement.

Source code:CLEOII_2002_I601701.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief eta' production in Upsilon(1S) decays class CLEOII_2002_I601701 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_2002_I601701);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");

  book(_hist, 1, 1, 3);
  book(_mult, 2, 1, 3);
  book(_weightSum, "TMP/weightSum");
}

/// 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 == 331) {
      unstable.push_back(p);
    }
    else if (!p.children().empty())
      findDecayProducts(p, unstable);
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // find the Upsilon(1S) mesons
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  Particles upsilons = ufs.particles(Cuts::pid == 553);
  if (upsilons.empty()) vetoEvent;
  // loop over them
  for (const Particle& ups : upsilons) {
    _weightSum->fill();
    Particles unstable;
    // Find the decay products we want
    findDecayProducts(ups, unstable);
    LorentzTransform cms_boost;
    if (ups.p3().mod() > 0.001)
      cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
    double mass = ups.mass();
    _mult->fill(unstable.size());
    // fill the spectrum
    for (const Particle& p : unstable) {
      FourMomentum p2 = cms_boost.transform(p.momentum());
      double xp = 2. * p2.E() / mass;
      _hist->fill(xp);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // spectrum
  if (_weightSum->val() > 0.) scale(_hist, 1. / *_weightSum);
  // BR
  scale(_mult, 1. / *_weightSum);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _hist;
CounterPtr _mult;
CounterPtr _weightSum;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_2002_I601701);

} ```