Rivet analyses

Λ0 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 pT with respect to the thrust axis for Λ0 baryon production at 29 GeV measured by the MARKII collaboration.

Source code:MARKII_1985_I209198.cc

// -*- 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);

}