Rivet analyses

title: DELPHI_1995_I394716

Strange baryon production in $Z$ hadronic decays at Delphi

Experiment: DELPHI (LEP 1)

Inspire ID: 394716

Status: VALIDATED

Authors: - Hendrik Hoeth

References: - Z. Phys. C, 67, 543--554 (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)

Measurement of the $\Xi^-$ and $\Sigma^+(1385)/\Sigma^-(1385)$ scaled momentum distributions by DELPHI at LEP 1. The paper also has the production cross-sections of these particles, but that's not implemented in Rivet.

Source code:DELPHI_1995_I394716.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 DELPHI strange baryon paper /// /// @author Hendrik Hoeth class DELPHI_1995_I394716 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_1995_I394716);


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

void init() {
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(UnstableParticles(), "UFS");

  book(_histXpXiMinus, 2, 1, 1);
  book(_histXpSigma1385Plus, 3, 1, 1);
  book(_weightedTotalNumXiMinus, "_weightedTotalNumXiMinus");
  book(_weightedTotalNumSigma1385Plus, "_weightedTotalNumSigma1385Plus");
}


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()) {
    const int id = p.abspid();
    switch (id) {
      case 3312:
        _histXpXiMinus->fill(p.p3().mod() / meanBeamMom);
        _weightedTotalNumXiMinus->fill();
        break;
      case 3114:
      case 3224:
        _histXpSigma1385Plus->fill(p.p3().mod() / meanBeamMom);
        _weightedTotalNumSigma1385Plus->fill();
        break;
    }
  }
}


/// Finalize
void finalize() {
  normalize(_histXpXiMinus, dbl(*_weightedTotalNumXiMinus) / sumOfWeights());
  normalize(_histXpSigma1385Plus, dbl(*_weightedTotalNumSigma1385Plus) / sumOfWeights());
}

/// @}

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.
CounterPtr _weightedTotalNumXiMinus;
CounterPtr _weightedTotalNumSigma1385Plus;

Histo1DPtr _histXpXiMinus;
Histo1DPtr _histXpSigma1385Plus;

};

RIVET_DECLARE_ALIASED_PLUGIN(DELPHI_1995_I394716, DELPHI_1995_S3137023);

} ```

Aliases: - DELPHI_1995_S3137023