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Rivet analyses reference

OPAL_1995_I393503

$K^0$ Production in Hadronic $Z^0$ Decays
Experiment: OPAL (LEP)
Inspire ID: 393503
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C67 (1995) 389-402, 1995
Beams: e+ e-
Beam energies: (45.6, 45.6) GeV
Run details:
  • Hadronic Z decay events generated on the Z pole ($\sqrt{s} = 91.2$ GeV)

The production of $K^0$ mesons measured using 1.3 million $Z^0$ events by the OPAL experiment at LEP. Only the fragmentation function is implemented.

Source code: OPAL_1995_I393503.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4#include "Rivet/Projections/ChargedFinalState.hh"
 5#include "Rivet/Projections/UnstableParticles.hh"
 6#include "Rivet/Projections/Beam.hh"
 7
 8namespace Rivet {
 9
10
11  /// @brief  kaon spectra at LEP1
12  class OPAL_1995_I393503 : public Analysis {
13  public:
14
15    /// Constructor
16    RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_1995_I393503);
17
18
19    /// @name Analysis methods
20    //@{
21
22    /// Book histograms and initialise projections before the run
23    void init() {
24      declare(Beam(), "Beams");
25      declare(ChargedFinalState(), "FS");
26      declare(UnstableParticles(), "UFS");
27
28      // Book histograms
29      book(_h_K0_x , 2, 1, 1);
30      book(_h_K0_xi, 3, 1, 1);
31
32    }
33
34
35    /// Perform the per-event analysis
36    void analyze(const Event& event) {
37
38      // First, veto on leptonic events by requiring at least 4 charged FS particles
39      const FinalState& fs = apply<FinalState>(event, "FS");
40      const size_t numParticles = fs.particles().size();
41
42      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
43      if (numParticles < 2) {
44        MSG_DEBUG("Failed leptonic event cut");
45        vetoEvent;
46      }
47      MSG_DEBUG("Passed leptonic event cut");
48
49      // Get beams and average beam momentum
50      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
51      const double meanBeamMom = ( beams.first.p3().mod() +
52                                   beams.second.p3().mod() ) / 2.0;
53      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
54
55      // Final state of unstable particles to get particle spectra
56      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
57
58      for (const Particle& p : ufs.particles(Cuts::pid==130 or
59					     Cuts::pid==310)) {
60        double xp = p.p3().mod()/meanBeamMom;
61	_h_K0_x->fill(xp);
62	_h_K0_xi->fill(-log(xp));
63      }
64
65    }
66
67
68    /// Normalise histograms etc., after the run
69    void finalize() {
70      scale(_h_K0_x, 1./sumOfWeights());
71      scale(_h_K0_xi, 1./sumOfWeights());
72    }
73
74    //@}
75
76
77    /// @name Histograms
78    //@{
79    Histo1DPtr _h_K0_x,_h_K0_xi;
80    //@}
81
82
83  };
84
85
86  // The hook for the plugin system
87  RIVET_DECLARE_PLUGIN(OPAL_1995_I393503);
88
89
90}