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. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

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 inferred. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: CELLO_1983_I191415.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5#include "Rivet/Projections/Beam.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// @brief pi0 and gamma spectra at 14, 22 and 34
 11  class CELLO_1983_I191415 : public Analysis {
 12  public:
 13
 14    /// Constructor
 15    RIVET_DEFAULT_ANALYSIS_CTOR(CELLO_1983_I191415);
 16
 17
 18    /// @name Analysis methods
 19    //@{
 20
 21    /// Book histograms and initialise projections before the run
 22    void init() {
 23
 24      // Initialise and register projections
 25      declare(Beam(), "Beams");
 26      declare(FinalState(), "FS");
 27      declare(UnstableParticles(), "UFS");
 28
 29      unsigned int iloc(0);
 30      if(isCompatibleWithSqrtS(14.)) {
 31	iloc=1;
 32      }
 33      else if (isCompatibleWithSqrtS(22.)) {
 34	iloc=2;
 35      }
 36      else if (isCompatibleWithSqrtS(34.)) {
 37	iloc=3;
 38      }
 39      else
 40	MSG_ERROR("Beam energy not supported!");
 41      // Book histograms
 42      book(_h_gamma, iloc  , 1, 1);
 43      book(_h_pi0  , iloc+3, 1, 1);
 44    }
 45
 46
 47    /// Perform the per-event analysis
 48    void analyze(const Event& event) {
 49      // at least 5 charged FS particles
 50      const FinalState& fs = apply<FinalState>(event, "FS");
 51      const size_t numParticles = fs.particles().size();
 52
 53      if (numParticles < 5) {
 54        MSG_DEBUG("Failed leptonic event cut");
 55        vetoEvent;
 56      }
 57      MSG_DEBUG("Passed leptonic event cut");
 58
 59      // Get beams and average beam momentum
 60      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
 61      const double meanBeamMom = ( beams.first.p3().mod() +
 62                                   beams.second.p3().mod() ) / 2.0;
 63      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
 64
 65      // Final state to get particle spectra
 66      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==111)) {
 67	double xE = p.E()/meanBeamMom;
 68	_h_pi0->fill(xE);
 69      }
 70      for (const Particle& p : apply<FinalState>(event, "FS").particles(Cuts::pid==22)) {
 71	double xE = p.E()/meanBeamMom;
 72	_h_gamma->fill(xE);
 73      }
 74    }
 75
 76
 77    /// Normalise histograms etc., after the run
 78    void finalize() {
 79
 80      double fact = sqr(sqrtS())/GeV2*crossSection()/microbarn/sumOfWeights();
 81      scale(_h_gamma, fact); 
 82      scale(_h_pi0  , fact); 
 83
 84    }
 85
 86    //@}
 87
 88
 89    /// @name Histograms
 90    //@{
 91    Histo1DPtr _h_gamma,_h_pi0;
 92    //@}
 93
 94
 95  };
 96
 97
 98  // The hook for the plugin system
 99  RIVET_DECLARE_PLUGIN(CELLO_1983_I191415);
100
101
102}