Rivet analyses

title: OPAL_2001_I536266

Charged particle multiplicities for u, d, s events at the Z pole

Experiment: OPAL (LEP)

Inspire ID: 536266

Status: VALIDATED

Authors: - Peter Richardson

References: - Eur.Phys.J. C19 (2001) 257-268

Beams: e+ e-

Beam energies: (45.6, 45.6)GeV

Run details: - Hadronic Z decay events at the Z pole

Measurements of the mean charged multiplicities separately for $d\bar d$, $u\bar u$ and $s\bar s$ initiated events in $e^+e^-$ interactions at the $Z^0$ mass.

Source code:OPAL_2001_I536266.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT

include "Rivet/Projections/InitialQuarks.hh"

namespace Rivet {

/// @brief multiplicities in u, d, s events class OPAL_2001_I536266 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2001_I536266);


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

/// Book histograms and initialise projections before the run
void init() {
  // Projections
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "CFS");
  declare(InitialQuarks(), "IQF");
  book(_wDown, "/TMP/WDOWN");
  book(_wUp, "/TMP/WUP");
  book(_wStrange, "/TMP/WSTRANGE");
  book(_hUp, 1, 1, 1);
  book(_hDown, 1, 1, 2);
  book(_hStrange, 1, 1, 3);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  const FinalState& cfs = apply<FinalState>(event, "CFS");
  if (cfs.size() < 2) vetoEvent;


  int flavour = 0;
  const InitialQuarks& iqf = apply<InitialQuarks>(event, "IQF");

  // If we only have two quarks (qqbar), just take the flavour.
  // If we have more than two quarks, look for the highest energetic q-qbar pair.
  if (iqf.particles().size() == 2) {
    flavour = iqf.particles().front().abspid();
  }
  else {
    map<int, double> quarkmap;
    for (const Particle& p : iqf.particles()) {
      if (quarkmap[p.pid()] < p.E()) {
        quarkmap[p.pid()] = p.E();
      }
    }
    double maxenergy = 0.;
    for (int i = 1; i <= 5; ++i) {
      if (quarkmap[i] + quarkmap[-i] > maxenergy) {
        flavour = i;
      }
    }
  }
  const size_t numParticles = cfs.particles().size();
  switch (flavour) {
    case 1:
      _wDown->fill();
      _hDown->fill(Ecm, numParticles);
      break;
    case 2:
      _wUp->fill();
      _hUp->fill(Ecm, numParticles);
      break;
    case 3:
      _wStrange->fill();
      _hStrange->fill(Ecm, numParticles);
      break;
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // calculate the averages and ratios
  if (_wUp->effNumEntries() != 0.) scale(_hUp, 1. / *_wUp);
  if (_wDown->effNumEntries() != 0.) scale(_hDown, 1. / *_wDown);
  if (_wStrange->effNumEntries() != 0.) scale(_hStrange, 1. / *_wStrange);

  BinnedEstimatePtr<string> ratioUD;
  book(ratioUD, 2, 1, 1);
  divide(_hUp, _hDown, ratioUD);

  BinnedEstimatePtr<string> ratioSD;
  book(ratioSD, 2, 1, 2);
  divide(_hStrange, _hDown, ratioSD);

  BinnedEstimatePtr<string> ratioSU;
  book(ratioSU, 2, 1, 3);
  divide(_hStrange, _hUp, ratioSU);
}

/// @}

/// @name Member variables
/// @{
CounterPtr _wDown, _wUp, _wStrange;
BinnedHistoPtr<string> _hDown, _hUp, _hStrange;
const string Ecm = "45.6";
/// @}

};

RIVET_DECLARE_PLUGIN(OPAL_2001_I536266);

} ```