Rivet analyses

title: DELPHI_1997_I428178

Flavour separated charged particle spectra at LEP1

Experiment: DELPHI (LEP)

Inspire ID: 428178

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B398 (1997) 194-206, 1997

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)

Charged particle momentum scaled momentum spectrum, separated into flavours of the initial quarks, at LEP1

Source code:DELPHI_1997_I428178.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 charged particle spectra class DELPHI_1997_I428178 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_1997_I428178);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(InitialQuarks(), "IQF");


  // Book histograms
  book(_h_bottom, 1, 1, 1);
  book(_h_charm, 1, 1, 2);
  book(_h_light, 1, 1, 3);

  book(_wBottom, "TMP/wBottom");
  book(_wCharm, "TMP/wCharm");
  book(_wLight, "TMP/wLight");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // First, veto on leptonic events by requiring at least 4 charged FS particles
  const FinalState& fs = apply<FinalState>(event, "FS");
  const size_t numParticles = fs.particles().size();

  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  if (numParticles < 2) {
    MSG_DEBUG("Failed leptonic event cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed leptonic event cut");

  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;
      }
    }
  }
  if (flavour == 5)
    _wBottom->fill();
  else if (flavour == 4)
    _wCharm->fill();
  else
    _wLight->fill();
  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
  const double meanBeamMom = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
  MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
  for (const Particle& p : fs.particles()) {
    double xp = p.p3().mod() / meanBeamMom;
    if (flavour == 5)
      _h_bottom->fill(xp);
    else if (flavour == 4)
      _h_charm->fill(xp);
    else
      _h_light->fill(xp);
  }
}


/// Normalise histograms etc., after the run
void finalize() {

  scale(_h_bottom, 1. / *_wBottom);
  scale(_h_charm, 1. / *_wCharm);
  scale(_h_light, 1. / *_wLight);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_bottom, _h_charm, _h_light;
CounterPtr _wBottom, _wCharm, _wLight;
/// @}

};

RIVET_DECLARE_PLUGIN(DELPHI_1997_I428178);

} ```