Rivet analyses

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

Experiment: BESIII (BEPC)

Inspire ID: 779017

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 659 (2008) 74-79

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- > hadrons

Measurement of the cross section for e+e− → light hadrons for $\sqrt{s}=3.65\to3.87\,$GeV. 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:BESIII_2008_I779017.cc

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

namespace Rivet {


  /// @brief e+ e- > light hadrons
  class BESIII_2008_I779017 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2008_I779017);


    /// @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 || Cuts::abspid == 431
                                || Cuts::abspid == 4122 || Cuts::abspid == 4232 || Cuts::abspid == 4132
                                || Cuts::abspid == 4332),
              "UFS");
      declare(FinalState(), "FS");

      // Book histograms
      book(_sigma, 1, 1, 1);
      _eCent = getOption<string>("ECENT", std::to_string(sqrtS() / GeV));
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      if (!ufs.particles().empty()) vetoEvent;
      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
        _sigma->fill(_eCent);
    }


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

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma;
    string _eCent;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2008_I779017);

}