Rivet analyses

title: SLD_2002_I582951

Measurement of the b-quark fragmentation function in $Z^0$ decays

Experiment: SLD (SLC)

Inspire ID: 582951

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys. Rev.D65:092006,2002 - hep-ex/0202031

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 SLC. The fragmentation function for weakly decaying $b$-quarks has been measured.

Source code:SLD_2002_I582951.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief SLD b-fragmentation measurement /// /// @author Peter Richardson class SLD_2002_I582951 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SLD_2002_I582951);


/// @name Helper functions
/// @note The PID:: namespace functions would be preferable, but don't have exactly the same behaviour. Preserving the original form.
/// @{
// bool isParton(int id) { return abs(id) <= 100 && abs(id) != 22 && (abs(id) < 11 || abs(id) > 18); }
// bool isBHadron(int id) { return ((abs(id)/100)%10 == 5) || (abs(id) >= 5000 && abs(id) <= 5999); }
/// @}


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

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

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


void analyze(const Event& e) {
  const FinalState& fs = apply<FinalState>(e, "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 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);


  for (ConstGenParticlePtr p : HepMCUtils::particles(e.genEvent())) {
    ConstGenVertexPtr dv = p->end_vertex();
    if (PID::isBottomHadron(p->pdg_id())) {
      const double xp = p->momentum().e() / meanBeamMom;

      // If the B-hadron has no B-hadron as a child, it decayed weakly:
      if (dv) {
        bool is_weak = true;
        for (ConstGenParticlePtr pp : HepMCUtils::particles(dv, Relatives::CHILDREN)) {
          if (PID::isBottomHadron(pp->pdg_id())) {
            is_weak = false;
          }
        }
        if (is_weak) {
          _histXbweak->fill(xp);
        }
      }
    }
  }
}


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

private:

/// Store the weighted sums of numbers of charged / charged+neutral
/// particles - used to calculate average number of particles for the
/// inclusive single particle distributions' normalisations.

Histo1DPtr _histXbweak;

/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(SLD_2002_I582951, SLD_2002_S4869273);

} ```

Aliases: - SLD_2002_S4869273