Rivet analyses

Inclusive analysis of the b quark fragmentation function in Z decays

Experiment: OPAL (LEP2)

Inspire ID: 599181

Status: VALIDATED

Authors: - Simone Amoroso

References: - Eur.Phys.J.C29:463-478,2003 - DOI: 10.1140/epjc/s2003-01229-x - arXiv: hep-ex/0210031

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)

A study of b quark fragmentation function is presented using inclusively reconstructed weakly decaying B hadrons. The measurement uses about four million hadronic Z decays recorded in 1992-2000 with the OPAL detector at LEP.

Source code:OPAL_2003_I599181.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief OPAL b-fragmentation measurement for weak B-hadron decays
  /// @author Simone Amoroso
  class OPAL_2003_I599181 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2003_I599181);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");

      // Book histograms
      book(_histXbweak, "TMP/hist", refData(1,1,1));

      book(_histMeanXbweak, 5, 1, 1);

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // 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);

      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      // Get Bottom hadrons
      const Particles bhads = select(ufs.particles(), isBottomHadron);

      for (const Particle& bhad : bhads) {
        // Check for weak decay, i.e. no more bottom present in children
        if (bhad.isLastWith(hasBottom)) {
          const double xp = bhad.E()/meanBeamMom;
          _histXbweak->fill(xp);
          _histMeanXbweak->fill("91.2", xp);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_histXbweak);
      Estimate1DPtr tmp;
      book(tmp,1,1,1);
      barchart(_histXbweak,tmp);
    }

    /// @}


  private:

    Histo1DPtr _histXbweak;
    BinnedProfilePtr<string> _histMeanXbweak;

  };



  RIVET_DECLARE_PLUGIN(OPAL_2003_I599181);


}