Rivet analyses

Cross section for e+e− → 3(π+π−) below 2 GeV by CMD3

Experiment: CMD3 (VEPP-2M)

Inspire ID: 1217420

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1302.0053

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons

Measurement of the cross section for e+e− → 3(π+π−) for energies below 2 GeV by the CMD3 experiment

Source code:CMD3_2013_I1217420.cc

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

namespace Rivet {


  /// @brief e+e- -> 3(pi+pi-)
  class CMD3_2013_I1217420 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2013_I1217420);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");

      // Book histograms
      for(unsigned int ix=0;ix<3;++ix)
        book(_sigma[ix],1,1,1+ix);

    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for(const Particle &child : p.children()) {
    if(child.children().empty()) {
      --nRes[child.pid()];
      --ncount;
    }
    else
      findChildren(child,nRes,ncount);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // find the final-state particles
      const FinalState& fs = apply<FinalState>(event, "FS");
      map<long,int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
      }
      if(ntotal==6 && nCount[211]==3 && nCount[-211]==3) {
        for(unsigned int ix=0;ix<3;++ix) _sigma[ix]->fill(round(sqrtS()/MeV));
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/nanobarn/sumOfWeights();
      for(unsigned int ix=0;ix<3;++ix)
        scale(_sigma[ix],fact);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<int> _sigma[3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(CMD3_2013_I1217420);


}