Rivet analyses

Cross section for hadron production for $\sqrt{s}=3.65\to3.87\,$GeV

Experiment: BESII (BEPC)

Inspire ID: 717720

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 121801

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- > hadrons

Measurement of the cross section for e+e− → hadrons for $\sqrt{s}=3.65\to3.87\,$GeV. In addition the cross section to charm hadrons near the ψ(3770) is measured. As the analyses requires the beam energy smearing described in the paper then central CMS energy should be specified using the ECENT (in GeV) option.

Source code:BESII_2006_I717720.cc

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

namespace Rivet {


  /// @brief e+ e- > hadrons
  class BESII_2006_I717720 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I717720);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(UnstableParticles(Cuts::abspid==411 ||
                Cuts::abspid==421 ), "UFS");
      declare(FinalState(), "FS");

      // Book histograms
      book(_sigma[0], 1,1,1);
      for(unsigned int ix=1;ix<4;++ix)
    book(_sigma[ix], 2,1,ix);
      string eCent = getOption<string>("ECENT", std::to_string(sqrtS()/GeV));
      double ee = std::stod(eCent);
      for(unsigned int ix=0;ix<3;++ix) {
        for(const auto & en : _sigma[ix].binning().edges<0>()) {
          if(fuzzyEquals(std::stod(en),ee,1e-5)) {
            _ecms[ix]=en;
            break;
          }
        }
      }
      if(_ecms[0].empty() && _ecms[1].empty() && _ecms[2].empty())
        MSG_ERROR("Beam energy incompatible with analysis.");
      _ecms[3]=_ecms[2];
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      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]) {
        vetoEvent;
      }
      else if(nCount[-11]==1 and nCount[11]==1 && ntotal==2+nCount[22]) {
        vetoEvent;
      }
      // everything else
      else {
        if(!_ecms[0].empty()) _sigma[0]->fill(_ecms[0]);
    if(!ufs.particles().empty()) {
      if(!_ecms[1].empty()) _sigma[1]->fill(_ecms[1]);
      if(ufs.particles()[0].abspid()==421) {
        if(!_ecms[2].empty()) _sigma[2]->fill(_ecms[2]);
          }
      else {
        if(!_ecms[3].empty()) _sigma[3]->fill(_ecms[3]);
          }
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/sumOfWeights()/nanobarn;
      for(unsigned int ix=0;ix<4;++ix)
        scale(_sigma[ix],fact);
    }

    /// @}

    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma[4];
    string _ecms[4];
    /// @}

  };


  RIVET_DECLARE_PLUGIN(BESII_2006_I717720);

}