Rivet analyses

title: OPAL_2003_I599181

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++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/UnstableParticles.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);

} ```