Rivet analyses

title: DELPHI_2011_I890503

Study of the b-quark fragmentation function at LEP 1

Experiment: DELPHI (LEP1)

Inspire ID: 890503

Status: VALIDATED

Authors: - Holger Schulz

References: - 10.1140/epjc/s10052-011-1557-x

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)

Measurement of the $b$-quark fragmentation function by DELPHI using 1994 LEP 1 data. The fragmentation function for weakly decaying $b$-quarks has been determined in a model independent way. Note --- this analysis supersedes DELPHI_2002_069_CONF_603.

Source code:DELPHI_2011_I890503.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

class DELPHI_2011_I890503 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_2011_I890503);


/// Book projections and histograms
void init() {
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(UnstableParticles(), "UFS");

  book(_histXbweak, 1, 1, 1);
  book(_histMeanXbweak, 2, 1, 1);
}


void analyze(const Event& e) {

  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  if (apply<FinalState>(e, "FS").particles().size() < 2) {
    MSG_DEBUG("Failed ncharged cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed ncharged cut");

  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(e, "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>(e, "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(Ecm, xp);
    }
  }
}


// Finalize
void finalize() {
  normalize(_histXbweak);
}

private:

Histo1DPtr _histXbweak;
BinnedProfilePtr<string> _histMeanXbweak;
const string Ecm = "91.2";

};

RIVET_DECLARE_PLUGIN(DELPHI_2011_I890503);

} ```