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JADE_1990_I282847

Photon, $\pi^0$ and $\eta$ spectra in $e^+e^-$ collisions at 35 and 44 GeV
Experiment: JADE (Petra)
Inspire ID: 282847
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C46 (1990) 1-7, 1990
Beams: e+ e-
Beam energies: (17.5, 17.5); (22.0, 22.0) GeV
Run details:
  • e+ e- to hadrons. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Measurement of the Photon, $\pi^0$ and $\eta$ spectra in $e^+e^-$ collisions at 35 and 44 GeV by the JADE experiment at Petra. The isolated photon spectrum which tests ISR and FST QED radiation is not implemented. The multiplicities are not implemented as they are in the PDG averages. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: JADE_1990_I282847.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 gamma, pi0 and eta spectra at 35 and 44 GeV
11  class JADE_1990_I282847 : public Analysis {
12  public:
13
14    /// Constructor
15    RIVET_DEFAULT_ANALYSIS_CTOR(JADE_1990_I282847);
16
17
18    /// @name Analysis methods
19    //@{
20
21    /// Book histograms and initialise projections before the run
22    void init() {
23      declare(Beam(), "Beams");
24      declare(FinalState(), "FS");
25      declare(UnstableParticles(), "UFS");
26
27      int ioff=-1;
28      if(isCompatibleWithSqrtS(35)) {
29      	ioff=0;
30      }
31      else if(isCompatibleWithSqrtS(44.)) {
32      	ioff=1;
33      }
34      else
35      	MSG_ERROR("Beam energy " << sqrtS() << " not supported!");
36      // Book histograms
37      book(_h_gamma, 1+ioff, 1, 1);
38      book(_h_pi0  , 3+ioff, 1, 1);
39      if(ioff==0) book(_h_eta, 5+ioff, 1, 1);
40    }
41
42
43    /// Perform the per-event analysis
44    void analyze(const Event& event) {
45      // Get beams and average beam momentum
46      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
47      const double meanBeamMom = ( beams.first.p3().mod() +
48                                   beams.second.p3().mod() ) / 2.0;
49      // gamma
50      const FinalState& fs = apply<FinalState>(event, "FS");
51      for (const Particle& p : fs.particles(Cuts::pid==22)) {
52      	double xE = p.E()/meanBeamMom;
53      	_h_gamma->fill(xE);
54      }
55      // pi0, eta
56      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
57      for (const Particle& p : ufs.particles(Cuts::pid==111 or Cuts::pid==221)) {
58      	double modp = p.p3().mod();
59      	double xE = p.E()/meanBeamMom;
60      	double beta = modp/p.E();
61      	if(p.pid()==111)
62      	  _h_pi0->fill(xE,1./beta);
63      	else if(_h_eta)
64      	  _h_eta->fill(xE,1./beta);
65      }
66    }
67
68
69    /// Normalise histograms etc., after the run
70    void finalize() {
71      scale(_h_gamma, crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
72      scale(_h_pi0  , crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
73      if(_h_eta) scale(_h_eta  , crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
74    }
75
76    //@}
77
78    /// @name Histograms
79    //@{
80    Histo1DPtr _h_gamma, _h_pi0, _h_eta;
81    //@}
82
83  };
84
85
86  // The hook for the plugin system
87  RIVET_DECLARE_PLUGIN(JADE_1990_I282847);
88
89
90}