Rivet analyses

Direct Photon Spectrum in Υ(1S) decays

Experiment: ARGUS (DORIS)

Inspire ID: 248655

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B 199 (1987) 291-296

Beams: * *

Beam energies: ANY

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

Measurement of the direct photon spectrum in Υ(1S) decays by the ARGUS experiment. While there is a more recent CLEO result that is not corrected for efficiency and resolution. The spectrum was read from the figures in the paper as it was not included in the original HEPDATA entry. The spectrum is not corrected for resolution and therefore the photon energies are smeared using the resolution given in the paper.

Source code:`ARGUS_1987_I248655.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 ARGUS_1987_I248655 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I248655);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::pid==553), "UFS");
      book(_h_gamma,2,1,1);
      book(_n_Ups,"TMP/nUps");
    }


    /// 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()) {
      _n_Ups->fill();
    }
    else if(nhadron!=0) {
      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,sqrt(sqr(0.072)+sqr(0.065)/E)*E);
        _h_gamma->fill(2.*E/ups.mass());
      }
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_gamma, 1./ *_n_Ups);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_gamma;
    CounterPtr _n_Ups;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(ARGUS_1987_I248655);

}

Rivet analyses

Direct Photon Spectrum in Υ(1S) decays

Source code:ARGUS_1987_I248655.cc

Source code:`ARGUS_1987_I248655.cc`