Rivet analyses

Charged particle multiplicities in heavy and light quark initiated events on the Z0 peak

Experiment: SLD (SLC)

Inspire ID: 422172

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B386:475-485,1996 - hep-ex/9608008

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)

Measurements of the mean charged multiplicities separately for bb̄, cc̄ and light quark (uds) initiated events in e+e− interactions at the Z0 mass.

Source code:SLD_1996_I422172.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/Sphericity.hh"
#include "Rivet/Projections/Thrust.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/ParisiTensor.hh"
#include "Rivet/Projections/Hemispheres.hh"
#include <cmath>

#define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT
#include "Rivet/Projections/InitialQuarks.hh"

namespace Rivet {


  /// @brief SLD multiplicities at mZ
  ///
  /// @author Peter Richardson
  class SLD_1996_I422172 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(SLD_1996_I422172);


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

    void init() {
      // Projections
      declare(Beam(), "Beams");
      declare(ChargedFinalState(), "CFS");
      declare(InitialQuarks(), "IQF");

      book(_h_bottom ,1, 1, 1);
      book(_h_charm  ,2, 1, 1);
      book(_h_light  ,3, 1, 1);

      book(_weightLight, "_weightLight");
      book(_weightCharm, "_weightCharm");
      book(_weightBottom, "_weightBottom");

      book(scatter_c, 4,1,1);
      book(scatter_b, 5,1,1);

    }


    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: case 2: case 3:
        _weightLight->fill();
        _h_light->fill(_h_light->bin(1).xMid(), numParticles);
        break;
      case 4:
        _weightCharm->fill();
        _h_charm->fill(_h_charm->bin(1).xMid(), numParticles);
        break;
      case 5:
        _weightBottom->fill();
        _h_bottom->fill(_h_bottom->bin(1).xMid(), numParticles);
        break;
      }

    }


    void multiplicity_subtract(const Histo1DPtr first, const Histo1DPtr second, Estimate1DPtr & estimate) {
      const auto diff = first->bin(1) - second->bin(1);
      estimate->bin(1).set(diff.sumW(), diff.errW());
    }


    void finalize() {
      if (_weightBottom->val()) scale(_h_bottom, 1./ *_weightBottom);
      if (_weightCharm->val())  scale(_h_charm,  1./ *_weightCharm );
      if (_weightLight->val())  scale(_h_light,  1./ *_weightLight );

      multiplicity_subtract(_h_charm,  _h_light, scatter_c);
      multiplicity_subtract(_h_bottom, _h_light, scatter_b);
    }

    /// @}


  private:

    /// Histograms
    Estimate1DPtr scatter_c, scatter_b;
    Histo1DPtr _h_bottom, _h_charm, _h_light;

    /// Weights
    CounterPtr _weightLight, _weightCharm, _weightBottom;

  };



  RIVET_DECLARE_ALIASED_PLUGIN(SLD_1996_I422172, SLD_1996_S3398250);

}

Aliases: - SLD_1996_S3398250