Rivet analyses

title: ALEPH_1991_I319520

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_I319520.cc

```c++ // -- 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_I319520 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(ALEPH_1991_I319520);


/// @name Analysis methods
/// @{

/// Book projections and histogram
void init() {
  const ChargedFinalState cfs;
  declare(cfs, "CFS");

  book(_histChTot, 1, 1, 1);
  book(_histAver, 2, 1, 1);
}


/// Do the analysis
void analyze(const Event& event) {
  const FinalState& cfs = apply<FinalState>(event, "CFS");
  MSG_DEBUG("Total charged multiplicity = " << cfs.size());
  _histChTot->fill(cfs.size());
  _histAver->fill(Ecms, cfs.size());
}


/// Normalize the histogram
void finalize() {
  scale(_histChTot, 1. / sumOfWeights()); // same as in ALEPH 1996
  scale(_histAver, 1. / sumOfWeights());
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<int> _histChTot;
BinnedHistoPtr<string> _histAver;
const string Ecms = "91.25";
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(ALEPH_1991_I319520, ALEPH_1991_S2435284);

} ```

Aliases: - ALEPH_1991_S2435284