Rivet analyses

Cross section for e+e− → ωπ+π− at energies between 1.4 and 2.2 GeV

Experiment: DM1 (DCI)

Inspire ID: 166964

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B106 (1981) 155-158, 1981

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for e+e− → ωπ+π− at energies between 1.4 and 2.2 GeV.

Source code:DM1_1981_I166964.cc

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

namespace Rivet {


  /// @brief e+e- > omega pi+pi-
  class DM1_1981_I166964 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(DM1_1981_I166964);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nomega, "TMP/omega" ,refData(1,1,1));
    }

    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) {
      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;
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
    if(p.children().empty()) continue;
    // find the omega
    if(p.pid()==223) {
      map<long,int> nRes = nCount;
      int ncount = ntotal;
      findChildren(p,nRes,ncount);
      // omega pi+pi-
      if(ncount!=2) continue;
      bool matched = true;
      for(auto const & val : nRes) {
        if(abs(val.first)==211) {
          if(val.second !=1) {
        matched = false;
        break;
          }
        }
        else if(val.second!=0) {
          matched = false;
          break;
        }
      }
      if(matched)
        _nomega->fill(sqrtS()/MeV);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/ sumOfWeights() /nanobarn;
      scale(_nomega,fact);
      Estimate1DPtr tmp;
      book(tmp,1,1,1);
      barchart(_nomega,tmp);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _nomega;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(DM1_1981_I166964);


}