Rivet analyses

Measurement of R for energies between 2.2324 to 3.6710 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1996394

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2112.11728

Beams: e- e+

Beam energies: (1.1, 1.1); (1.2, 1.2); (1.4, 1.4); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.7, 1.7); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8)GeV

Run details: - e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of R and the hadronic cross section in e+e− collisions by BESIII for energies between 2.2324 to 3.6710 GeV. The muonic cross section is also outputted to the yoda file so that ratio R can be recalculated if runs are combined.

Source code:BESIII_2021_I1996394.cc

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

namespace Rivet {


  /// @brief measurement of R 2.2324 to 3.6710 GeV
  class BESIII_2021_I1996394 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1996394);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");

      // Book histograms
      book(_c_hadrons, "/TMP/sigma_hadrons", refData<YODA::BinnedEstimate<string>>(1,1,1));
      book(_c_muons,   "/TMP/sigma_muons"  , refData<YODA::BinnedEstimate<string>>(1,1,1));
      for (const string& en : _c_hadrons.binning().edges<0>()) {
        double eval = stod(en);
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en; break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }


    /// 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;
      }
      // mu+mu- + photons
      if (nCount[-13]==1 and nCount[13]==1 && ntotal==2+nCount[22]) {
        _c_muons->fill(_sqs);
      }
      else { // everything else
        _c_hadrons->fill(_sqs);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      BinnedEstimatePtr<string> mult;
      book(mult, 1, 1, 1);
      divide(_c_hadrons,_c_muons,mult);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _c_hadrons, _c_muons;
    string _sqs = "";
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2021_I1996394);

}