Rivet analyses

Direct Photon Spectrum in Υ(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 Υ(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 Υ(1S) decays

Source code:CLEO_1986_I220652.cc

Source code:`CLEO_1986_I220652.cc`