Rivet analyses

Cross-sections for light hadrons at 3.650 and 3.773 GeV

Experiment: BESII (BEPC)

Inspire ID: 762901

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B656 (2007) 30-37, 2007

Beams: e+ e-

Beam energies: (1.8, 1.8); (1.9, 1.9)GeV

Run details: - e+e- to hadrons

Cross section for e⁺e⁻ → 2π⁺2π⁻K⁺K⁻, π⁺π⁻2K⁺2K⁻, 2π⁺2π⁻pp̄, 3π⁺3π⁻, 2π⁺2π⁻K⁺K⁻π⁰, ρ⁰π⁺π⁻, ρ⁰K⁺K⁻, ρ⁰pp̄, K^*0K⁻π⁺ + c.c. at 3.650 and 3.773 GeV.

Source code:`BESII_2007_I762901.cc`

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

namespace Rivet {


  /// @brief Cross-sections for light hadrons at 3.650 and 3.773 GeV
  class BESII_2007_I762901 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2007_I762901);


    /// @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 (size_t ix=1; ix<11; ++ix) {
        if (ix==6) continue;
        book(_nMeson[ix], 1, 1, ix);
      }
      for (const string& en : _nMeson[1].binning().edges<0>()) {
        const double eval = stod(en)*GeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en; break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) const {
      for (const Particle &child : p.children()) {
        if (child.children().empty()) {
          nRes[child.pid()]-=1;
          --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;
      }
      if (ntotal==6) {
        if (nCount[211]==2 && nCount[-211]==2 &&
            nCount[321]==1 && nCount[-321]==1)  _nMeson[1]->fill(_sqs);
        else if (nCount[211]==1 && nCount[-211]==1 &&
                 nCount[321]==2 && nCount[-321]==2) {
          if (_sqs=="3.773") _nMeson[2]->fill(_sqs);
        }
        else if (nCount[211]==2 && nCount[-211]==2 &&
                 nCount[2212]==1 && nCount[-2212]==1) _nMeson[3]->fill(_sqs);
        else if (nCount[211]==3 && nCount[-211]==3)   _nMeson[4]->fill(_sqs);
      }
      else if (ntotal==7) {
        if (nCount[211]==2 && nCount[-211]==2 &&
            nCount[321]==1 && nCount[-321]==1 && nCount[111]==1) _nMeson[5]->fill(_sqs);
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        if (p.pid()!=113 && p.abspid()!=313) continue;
        map<long,int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p,nRes,ncount);
        if (p.pid()==113) {
          if (ncount!=2) continue;
          unsigned int nPi(0), nK(0), nProt(0);
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first)==211 && val.second==1) {
              nPi+=1;
            }
            else if (abs(val.first)==321 && val.second==1) {
              nK+=1;
            }
            else if (abs(val.first)==2212 && val.second==1) {
              nProt+=1;
            }
            else if (val.second!=0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            if(nProt==2 && nPi==0 && nK==0)       _nMeson[9]->fill(_sqs);
            else if(nProt==0 && nPi==2 && nK==0)  _nMeson[7]->fill(_sqs);
            else if(nProt==0 && nPi==0 && nK==2)  _nMeson[8]->fill(_sqs);
          }
        }
        else if (p.abspid()==313) {
          if (ncount!=2) continue;
          unsigned int npi(0),nK(0);
          bool matched = true;
          int ipi = p.pid()==313 ?  211 : -211;
          int iK  = p.pid()==313 ? -321 :  321;
          for(const auto& val : nRes) {
            if (abs(val.first)== ipi && val.second==1) {
              npi+=1;
            }
            else if (abs(val.first)==iK && val.second==1) {
              nK+=1;
            }
            else if (val.second!=0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            if(npi==1&&nK==1)  _nMeson[10]->fill(_sqs);
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_nMeson, crossSection()/ sumOfWeights() /picobarn);
    }

    /// @}


    /// @name Histograms
    /// @{
    map<int,BinnedHistoPtr<string>> _nMeson;
    string _sqs = "";
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESII_2007_I762901);

}

Rivet analyses

Cross-sections for light hadrons at 3.650 and 3.773 GeV

Source code:BESII_2007_I762901.cc

Source code:`BESII_2007_I762901.cc`