Rivet analyses

Cross Section for e⁺e⁻ → π⁺π⁻h_c for energies between 3.89 and 4.6 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1494065

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 118 (2017) no.9, 092002

Beams: e+ e-

Beam energies: (1.9, 1.9); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3)GeV

Run details: - e+ e- to hadrons

Cross section for e⁺e⁻ → π⁺π⁻h_c for energies between 3.89 and 4.6 GeV measured by the BESIII collaboration.

Source code:`BESIII_2017_I1494065.cc`

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

namespace Rivet {


  /// @brief e+ e- > pi+ pi- h_c
  class BESIII_2017_I1494065 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1494065);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::pid==10443), "UFS");
      for (size_t ix=0; ix<2; ++ix) {
        book(_nhc[ix], 1+ix, 1, 1);
        for (const string& en : _nhc[ix].binning().edges<0>()) {
          const double eval = stod(en);
          if (isCompatibleWithSqrtS(eval)) {
            _sqs[ix] = en; break;
          }
        }
      }
      raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].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()];
          --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");
      // loop over the h_c
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        map<long,int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p,nRes,ncount);
        // h_c pi+pi-
        if (ncount!=2) continue;
        bool matched = true;
        for (const auto& val : nRes) {
          if (abs(val.first)==211) {
            if (val.second !=1) {
              matched = false;
              break;
            }
          }
          else if (val.second!=0) {
            matched = false;
            break;
          }
        }
        if (matched) {
          _nhc[0]->fill(_sqs[0]);
          _nhc[1]->fill(_sqs[1]);
          break;
        }
      }
    }

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

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _nhc[2];
    string _sqs[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2017_I1494065);

}

Rivet analyses

Cross Section for e+e− → π+π−hc for energies between 3.89 and 4.6 GeV

Source code:BESIII_2017_I1494065.cc

Cross Section for e⁺e⁻ → π⁺π⁻h_c for energies between 3.89 and 4.6 GeV

Source code:`BESIII_2017_I1494065.cc`