Rivet analyses

title: CLEO_1986_I220652

Direct Photon Spectrum in $\Upsilon(1S)$ decays

Experiment: CLEO (CESR)

Inspire ID: 220652

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 56 (1986) 1222

Beams: * *

Beam energies: ANY

Run details: - Any process producing Upsilon mesons, original e+e- collisions

Measurement of the direct photon spectrum in $\Upsilon(1S)$ decays by CLEO. The spectrum was read from the figures in the paper as it was not included in the original HEPDATA entry and is not corrected for efficiency/resolution. The energy smearing given in the paper is applied to the photon energies

Source code:CLEO_1986_I220652.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

include "Rivet/Tools/Random.hh"

namespace Rivet {

/// @brief Direct photon spectrum in upslion decay class CLEO_1986_I220652 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_1986_I220652);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::pid == 553), "UFS");
  // histos
  book(_h, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // Find the Upsilons among the unstables
  for (const Particle& ups : apply<UnstableParticles>(event, "UFS").particles()) {
    unsigned int nhadron(0);
    Particles photons;
    for (const Particle& child : ups.children()) {
      if (PID::isHadron(child.pid()))
        ++nhadron;
      else if (child.pid() == PID::PHOTON)
        photons.push_back(child);
    }
    if (nhadron == 0 || photons.empty()) continue;
    LorentzTransform boost;
    if (ups.p3().mod() > 1 * MeV)
      boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
    for (const Particle& gamma : photons) {
      double E = boost.transform(gamma.momentum()).E();
      E = randnorm(E, 0.21 * sqrt(E));
      _h->fill(2. * E / ups.mass());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEO_1986_I220652);

} ```