rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

CELLO_1983_I191415

Photon and $\pi^0$ spectra in $e^+e^-$ at 14, 22 and 34 GeV
Experiment: CELLO (Petra)
Inspire ID: 191415
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C20 (1983) 207, 1983
Beams: e+ e-
Beam energies: (7.0, 7.0); (11.0, 11.0); (17.0, 17.0) GeV
Run details:
  • e+ e- to hadrons

Measurement of the $\gamma$ and $\pi^0$ energy fractions in $e^+e^-$ collisions for centre-of-mass energies of 14, 22 and 34 GeV by the CELLO experiment at Petra. Only the bin centroids are given in the paper and HEPdata so the bin widths have been infered.

Source code: CELLO_1983_I191415.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief pi0 and gamma spectra at 14, 22 and 34
  class CELLO_1983_I191415 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(CELLO_1983_I191415);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");

      unsigned int iloc(0);
      if(fuzzyEquals(sqrtS()/GeV, 14., 1e-3)) {
	iloc=1;
      }
      else if (fuzzyEquals(sqrtS()/GeV, 22., 1e-3)) {
	iloc=2;
      }
      else if (fuzzyEquals(sqrtS()/GeV, 34., 1e-3)) {
	iloc=3;
      }
      else
	MSG_ERROR("Beam energy not supported!");
      // Book histograms
      book(_h_gamma, iloc  , 1, 1);
      book(_h_pi0  , iloc+3, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // at least 5 charged FS particles
      const FinalState& fs = apply<FinalState>(event, "FS");
      const size_t numParticles = fs.particles().size();

      if (numParticles < 5) {
        MSG_DEBUG("Failed leptonic event cut");
        vetoEvent;
      }
      MSG_DEBUG("Passed leptonic event cut");

      // Get beams and average beam momentum
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double meanBeamMom = ( beams.first.p3().mod() +
                                   beams.second.p3().mod() ) / 2.0;
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

      // Final state to get particle spectra
      for (const Particle& p : apply<UnstableFinalState>(event, "UFS").particles(Cuts::pid==111)) {
	double xE = p.E()/meanBeamMom;
	_h_pi0->fill(xE);
      }
      for (const Particle& p : apply<FinalState>(event, "FS").particles(Cuts::pid==22)) {
	double xE = p.E()/meanBeamMom;
	_h_gamma->fill(xE);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      double fact = sqr(sqrtS())/GeV2*crossSection()/microbarn/sumOfWeights();
      scale(_h_gamma, fact); 
      scale(_h_pi0  , fact); 

    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_gamma,_h_pi0;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CELLO_1983_I191415);


}