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ALEPH_1991_S2435284

Hadronic Z decay charged multiplicity measurement
Experiment: ALEPH (LEP 1)
Inspire ID: 319520
Status: VALIDATED
Authors:
  • Andy Buckley
References:
  • Phys. Lett. B, 273, 181 (1991)
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 charged particle multiplicity distribution of hadronic Z decays, as measured on the peak of the Z resonance using the ALEPH detector at LEP. The unfolding procedure was model independent, and the distribution was found to have a mean of $20.85 \pm 0.24$, Comparison with lower energy data supports the KNO scaling hypothesis. The shape of the multiplicity distribution is well described by a log-normal distribution, as predicted from a cascading model for multi-particle production.

Source code: ALEPH_1991_S2435284.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/ChargedFinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief ALEPH LEP1 charged multiplicity in hadronic Z decay
 9  ///
10  /// @author Andy Buckley
11  class ALEPH_1991_S2435284 : public Analysis {
12  public:
13
14    RIVET_DEFAULT_ANALYSIS_CTOR(ALEPH_1991_S2435284);
15
16
17    /// @name Analysis methods
18    /// @{
19
20    /// Book projections and histogram
21    void init() {
22      const ChargedFinalState cfs;
23      declare(cfs, "CFS");
24
25      book(_histChTot ,1, 1, 1);
26      book(_histAver, 2, 1, 1);
27    }
28
29
30    /// Do the analysis
31    void analyze(const Event& event) {
32      const FinalState& cfs = apply<FinalState>(event, "CFS");
33      MSG_DEBUG("Total charged multiplicity = " << cfs.size());
34      _histChTot->fill(cfs.size());
35      _histAver->fill(_histAver->bin(0).xMid(),cfs.size());
36    }
37
38
39    /// Normalize the histogram
40    void finalize() {
41      scale(_histChTot, 2.0/sumOfWeights()); // same as in ALEPH 1996
42      scale(_histAver , 1./sumOfWeights());
43    }
44
45    /// @}
46
47
48    /// @name Histograms
49    /// @{
50    Histo1DPtr _histChTot;
51    Histo1DPtr _histAver;
52    /// @}
53
54  };
55
56
57
58  RIVET_DECLARE_ALIASED_PLUGIN(ALEPH_1991_S2435284, ALEPH_1991_I319520);
59
60}