Rivet analyses

title: OPAL_1997_I421978

Strange baryon production in $Z$ hadronic decays at OPAL

Experiment: OPAL (LEP 1)

Inspire ID: 421978

Status: VALIDATED

Authors: - Peter Richardson

References: - Z. Phys. C, 73, 569--586 (1997)

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 $\Xi^-$, $\Lambda^0$, $\Sigma^+(1385)$, $\Sigma^-(1385)$, $\Xi^0(1530)$ and $\Lambda^0(1520)$ scaled momentum distributions by OPAL at LEP 1. The paper also has the production cross-sections of these particles, but that is not implemented in Rivet.

Source code:OPAL_1997_I421978.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 strange baryon paper /// /// @author Peter Richardson class OPAL_1997_I421978 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_1997_I421978);


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

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

  book(_histXpLambda, 1, 1, 1);
  book(_histXiLambda, 2, 1, 1);
  book(_histXpXiMinus, 3, 1, 1);
  book(_histXiXiMinus, 4, 1, 1);
  book(_histXpSigma1385Plus, 5, 1, 1);
  book(_histXiSigma1385Plus, 6, 1, 1);
  book(_histXpSigma1385Minus, 7, 1, 1);
  book(_histXiSigma1385Minus, 8, 1, 1);
  book(_histXpXi1530, 9, 1, 1);
  book(_histXiXi1530, 10, 1, 1);
  book(_histXpLambda1520, 11, 1, 1);
  book(_histXiLambda1520, 12, 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()) {
    const int id = p.abspid();
    if (!inRange(id, 3000, 3999) && id != 102134) continue;

    const double xE = p.E() / meanBeamMom;
    const double xp = p.p3().mod() / (2 * meanBeamMom);
    const double xi = -log(xp);

    switch (id) {
      case 3312:
        _histXpXiMinus->fill(xE);
        _histXiXiMinus->fill(xi);
        break;
      case 3224:
        _histXpSigma1385Plus->fill(xE);
        _histXiSigma1385Plus->fill(xi);
        break;
      case 3114:
        _histXpSigma1385Minus->fill(xE);
        _histXiSigma1385Minus->fill(xi);
        break;
      case 3122:
        _histXpLambda->fill(xE);
        _histXiLambda->fill(xi);
        break;
      case 3324:
        _histXpXi1530->fill(xE);
        _histXiXi1530->fill(xi);
        break;
      case 102134:
        _histXpLambda1520->fill(xE);
        _histXiLambda1520->fill(xi);
        break;
    }
  }
}


/// Finalize
void finalize() {
  double fact = 1. / sumOfWeights();
  scale(_histXpLambda, fact);
  scale(_histXiLambda, fact);
  scale(_histXpXiMinus, fact);
  scale(_histXiXiMinus, fact);
  scale(_histXpSigma1385Plus, fact);
  scale(_histXiSigma1385Plus, fact);
  scale(_histXpSigma1385Minus, fact);
  scale(_histXiSigma1385Minus, fact);
  scale(_histXpXi1530, fact);
  scale(_histXiXi1530, fact);
  scale(_histXpLambda1520, fact);
  scale(_histXiLambda1520, fact);
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _histXpLambda;
Histo1DPtr _histXiLambda;
Histo1DPtr _histXpXiMinus;
Histo1DPtr _histXiXiMinus;
Histo1DPtr _histXpSigma1385Plus;
Histo1DPtr _histXiSigma1385Plus;
Histo1DPtr _histXpSigma1385Minus;
Histo1DPtr _histXiSigma1385Minus;
Histo1DPtr _histXpXi1530;
Histo1DPtr _histXiXi1530;
Histo1DPtr _histXpLambda1520;
Histo1DPtr _histXiLambda1520;
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(OPAL_1997_I421978, OPAL_1997_S3396100);

} ```

Aliases: - OPAL_1997_S3396100