Rivet analyses

title: OPAL_1995_I398320

$\Delta^{++}$ Production in Hadronic $Z^0$ Decays

Experiment: OPAL (LEP 1)

Inspire ID: 398320

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B358:162-172,1995

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)

The production of $\Delta^{++}$ baryons measured using 3.5 million $Z^0$ events by the OPAL experiment at LEP. Only the fragmentation function is implemented.

Source code:OPAL_1995_I398320.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 {

/// @brief OPAL Delta++ fragmentation function paper /// /// @author Peter Richardson class OPAL_1995_I398320 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_1995_I398320);


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

void init() {
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  book(_histXpDelta, 1, 1, 1);
}


void analyze(const Event& e) {
  // First, veto on leptonic events by requiring at least 4 charged FS particles
  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 leptonic event cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed leptonic event 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);

  // Final state of unstable particles to get particle spectra
  const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");

  for (const Particle& p : ufs.particles()) {
    if (p.abspid() == 2224) {
      double xp = p.p3().mod() / meanBeamMom;
      _histXpDelta->fill(xp);
    }
  }
}


/// Finalize
void finalize() {
  scale(_histXpDelta, 1. / sumOfWeights());
}

/// @}

private:

Histo1DPtr _histXpDelta;

};

RIVET_DECLARE_ALIASED_PLUGIN(OPAL_1995_I398320, OPAL_1995_S3198391);

} ```

Aliases: - OPAL_1995_S3198391