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## Rivet analyses reference

### 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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/ChargedFinalState.hh" namespace Rivet { /// @brief ALEPH LEP1 charged multiplicity in hadronic Z decay /// @author Andy Buckley class ALEPH_1991_S2435284 : public Analysis { public: /// Constructor. ALEPH_1991_S2435284() : Analysis("ALEPH_1991_S2435284") { } /// @name Analysis methods //@{ /// Book projections and histogram void init() { const ChargedFinalState cfs; declare(cfs, "CFS"); _histChTot = bookHisto1D(1, 1, 1); _histAver = bookHisto1D(2, 1, 1); } /// Do the analysis void analyze(const Event& event) { const FinalState& cfs = apply(event, "CFS"); MSG_DEBUG("Total charged multiplicity = " << cfs.size()); _histChTot->fill(cfs.size(), event.weight()); _histAver->fill(_histAver->bin(0).xMid(),cfs.size()*event.weight()); } /// Normalize the histogram void finalize() { scale(_histChTot, 2.0/sumOfWeights()); // same as in ALEPH 1996 scale(_histAver , 1./sumOfWeights()); } //@} private: /// @name Histograms //@{ Histo1DPtr _histChTot; Histo1DPtr _histAver; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ALEPH_1991_S2435284); }