Rivet analyses

Spectra for strange hadron production at ECMS = 35 GeV

Experiment: CELLO (Petra)

Inspire ID: 283026

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C46 (1990) 397-404, 1990

Beams: e+ e-

Beam energies: (17.5, 17.5)GeV

Run details: - e+e- to hadrons at 35 GeV

Spectra for K0, K*+ and Λ production in e+e− collisions at a centre-of-mass energy of 35 GeV measured by the CELLO experiment at Petra. The data in HEPData only contains the centroids of the bins, not the bin edges which have therefore been inferred.

Source code:CELLO_1990_I283026.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief Strange hadrons at 35GeV
  class CELLO_1990_I283026 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CELLO_1990_I283026);


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

    /// Book histograms and initialise projections before the run
    void init() {

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

      // Book histograms
      book(_h["K0"],     1, 1, 1);
      book(_h["Kstar"],  2, 1, 1);
      book(_h["Lambda"], 3, 1, 1);

      _axes["K0"] = YODA::Axis<double>({0.0315, 0.0365, 0.0535, 0.0745, 0.0955, 0.1165,
                                        0.1415, 0.175, 0.2375, 0.282, 0.3775, 0.652});
      _axes["Kstar"] = YODA::Axis<double>({0.055, 0.195, 0.335, 0.537, 0.883});
      _axes["Lambda"] = YODA::Axis<double>({0.067, 0.085, 0.103, 0.131, 0.175, 0.269, 0.447, 0.723});

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      if (_edges.empty()) {
        for (const auto& item : _h) {
          _edges[item.first] = item.second->xEdges();
        }
      }

      // First, veto on leptonic events by requiring at least 4 charged FS particles
      const FinalState& fs = apply<FinalState>(event, "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>(event, "Beams").beams();
      const double meanBeamMom = 0.5*(beams.first.p3().mod() + beams.second.p3().mod());
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

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

      for (const Particle& p : ufs.particles()) {
        const int id = p.abspid();
        if (id == PID::K0S || id == PID::K0L) {
          discfill("K0", p.E()/meanBeamMom);
        }
        else if(abs(id)==323) {
          discfill("Kstar", p.E()/meanBeamMom);
        }
        else if(abs(id)==3122) {
          discfill("Lambda", p.E()/meanBeamMom);
        }
      }
    }

    void discfill(const string& name, const double value) {
      string edge = "OTHER";
      const size_t idx = _axes[name].index(value);
      if (idx && idx <= _edges[name].size())  edge = _edges[name][idx-1];
      _h[name]->fill(edge);
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h, 1./sumOfWeights());
      for( auto & hist : _h) {
        for(auto & b: hist.second->bins()) {
          const size_t idx = b.index();
          b.scaleW(1./_axes[hist.first].width(idx));
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    map<string, BinnedHistoPtr<string>> _h;
    map<string, YODA::Axis<double>> _axes;
    map<string, vector<string>> _edges;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(CELLO_1990_I283026);


}