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OPAL_2003_I599181

Inclusive analysis of the b quark fragmentation function in Z decays
Experiment: OPAL (LEP2)
Inspire ID: 599181
Status: VALIDATED
Authors:
  • Simone Amoroso
References: 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)

A study of b quark fragmentation function is presented using inclusively reconstructed weakly decaying B hadrons. The measurement uses about four million hadronic Z decays recorded in 1992-2000 with the OPAL detector at LEP.

Source code: OPAL_2003_I599181.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4#include "Rivet/Projections/Beam.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// @brief OPAL b-fragmentation measurement for weak B-hadron decays
10  /// @author Simone Amoroso
11  class OPAL_2003_I599181 : public Analysis {
12  public:
13
14    /// Constructor
15    RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2003_I599181);
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(UnstableParticles(), "UFS");
27
28      // Book histograms
29      book(_histXbweak     ,1, 1, 1);
30      book(_histMeanXbweak ,2, 1, 1);
31
32    }
33
34
35    /// Perform the per-event analysis
36    void analyze(const Event& event) {
37
38      // Get beams and average beam momentum
39      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
40      const double meanBeamMom = ( beams.first.p3().mod() +beams.second.p3().mod() ) / 2.0;
41      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
42
43      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
44      // Get Bottom hadrons
45      const Particles bhads = filter_select(ufs.particles(), isBottomHadron);
46
47      for (const Particle& bhad : bhads) {
48        // Check for weak decay, i.e. no more bottom present in children
49        if (bhad.children(lastParticleWith(hasBottom)).empty()) {
50          const double xp = bhad.E()/meanBeamMom;
51          _histXbweak->fill(xp);
52          _histMeanXbweak->fill(_histMeanXbweak->bin(0).xMid(), xp);
53        }
54      }
55    }
56
57
58    /// Normalise histograms etc., after the run
59    void finalize() {
60      normalize(_histXbweak);
61    }
62
63    //@}
64
65
66  private:
67
68    Histo1DPtr _histXbweak;
69    Profile1DPtr _histMeanXbweak;
70
71  };
72
73
74
75  // The hook for the plugin system
76  RIVET_DECLARE_PLUGIN(OPAL_2003_I599181);
77
78
79}