Rivet analyses

title: MARKII_1985_I209198

$\Lambda^0$ production at 29 GeV

Experiment: MARKII (PEP)

Inspire ID: 209198

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 54 (1985) 2071-2074, 1985

Beams: e+ e-

Beam energies: (14.5, 14.5)GeV

Run details: - e+ e- to hadrons at 29 GeV

Spectrum and $p_T$ with respect to the thrust axis for $\Lambda^0$ baryon production at 29 GeV measured by the MARKII collaboration.

Source code:MARKII_1985_I209198.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/Thrust.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda0 production at 29 GeV class MARKII_1985_I209198 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1985_I209198);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(), "UFS");
  const ChargedFinalState cfs;
  declare(cfs, "CFS");
  const FinalState fs;
  declare(cfs, "FS");
  declare(Thrust(fs), "Thrust");
  //Histograms
  book(_h_spect, 2, 1, 1);
  book(_h_pT, 3, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  if (_edges.empty()) _edges = _h_spect->xEdges();
  // 5 charged particles
  const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
  if (cfs.particles().size() < 5) vetoEvent;
  // thrust
  const Thrust& thrust = apply<Thrust>(event, "Thrust");
  // lambdas
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles(Cuts::abspid == 3122)) {
    const double xp = 2. * p.E() / sqrtS();
    Vector3 mom3 = p.p3();
    const double beta = mom3.mod() / p.E();
    const double pTin = dot(mom3, thrust.thrustMajorAxis());
    const double pTout = dot(mom3, thrust.thrustMinorAxis());
    const double pT2 = sqr(pTin) + sqr(pTout);
    const size_t idx = _axis.index(xp);
    string edge = "OTHER";
    if (idx && idx <= _axis.numBins()) edge = _edges[idx - 1];
    _h_spect->fill(edge, 1. / beta);
    _h_pT->fill(pT2);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_spect, sqr(sqrtS()) * crossSection() / nanobarn / sumOfWeights());
  normalize(_h_pT);
  for (auto& b : _h_spect->bins()) {
    const size_t idx = b.index();
    b.scaleW(1. / _axis.width(idx));
  }
}

///@}


/// @name Histograms
///@{
BinnedHistoPtr<string> _h_spect;
Histo1DPtr _h_pT;
vector<string> _edges;
YODA::Axis<double> _axis{0.084, 0.094, 0.104, 0.124, 0.157, 0.190, 0.223, 0.256,
                         0.289, 0.322, 0.355, 0.423, 0.491, 0.559, 0.627, 0.695};
///@}

};

RIVET_DECLARE_PLUGIN(MARKII_1985_I209198);

} ```