Rivet analyses

Measurement of the cross section for e+e− → 2p2p̄ for ECMS between 4 and 4.6 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1837725

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2012.11079

Beams: e+ e-

Beam energies: (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); (2.2, 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)GeV

Run details: - e+ e- to hadrons

Measurement of the cross section for e+e− → 2p2p̄ for ECMS between 4 and 4.6 GeV by the BESIII collaboration.

Source code:BESIII_2020_I1837725.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/LeptonFinder.hh"
#include "Rivet/Projections/MissingMomentum.hh"
#include "Rivet/Projections/PromptFinalState.hh"

namespace Rivet {


  /// @brief e+e- > 2p 2pbar
  class BESIII_2020_I1837725 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1837725);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(FinalState(), "FS");

      // Book histograms
      book(_nproton, 1, 1, 1);
      for (const string& en : _nproton.binning().edges<0>()) {
        const 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");
      if (fs.particles().size()!=4) vetoEvent;
      for (const Particle& p : fs.particles()) {
        if (p.abspid()!=PID::PROTON) vetoEvent;
      }
      _nproton->fill(_sqs);
    }


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

    ///@}


    /// @name Histograms
    ///@{
    BinnedHistoPtr<string> _nproton;
    string _sqs = "";
    ///@}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2020_I1837725);

}