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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(_estXbweak, 1, 1, 1);
30      book(_histXbweak, "/TMP/Xbweak", refData(1, 1, 1));
31
32      book(_histMeanXbweak, 2, 1, 1);
33
34    }
35
36
37    /// Perform the per-event analysis
38    void analyze(const Event& event) {
39
40      // Get beams and average beam momentum
41      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
42      const double meanBeamMom = ( beams.first.p3().mod() +beams.second.p3().mod() ) / 2.0;
43      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
44
45      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
46      // Get Bottom hadrons
47      const Particles bhads = select(ufs.particles(), isBottomHadron);
48
49      for (const Particle& bhad : bhads) {
50        // Check for weak decay, i.e. no more bottom present in children
51        if (bhad.isLastWith(hasBottom)) {
52          const double xp = bhad.E()/meanBeamMom;
53          _histXbweak->fill(xp);
54          _histMeanXbweak->fill(_histMeanXbweak->bin(1).xMid(), xp);
55        }
56      }
57    }
58
59
60    /// Normalise histograms etc., after the run
61    void finalize() {
62      normalize(_histXbweak);
63      barchart(_histXbweak, _estXbweak);
64    }
65
66    /// @}
67
68
69  private:
70
71    Histo1DPtr _histXbweak;
72    Estimate1DPtr _estXbweak;
73    Profile1DPtr _histMeanXbweak;
74
75  };
76
77
78
79  RIVET_DECLARE_PLUGIN(OPAL_2003_I599181);
80
81
82}