Rivet analyses

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++ -*-
#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);

}

Rivet analyses

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

Source code:CLEO_1986_I220652.cc

Source code:`CLEO_1986_I220652.cc`