Rivet analyses

title: BESIII_2020_I1837725

Measurement of the cross section for $e^+e^-\to2p2\bar{p}$ for $E_{\text{CMS}}$ 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 $e^+e^-\to2p2\bar{p}$ for $E_{\text{CMS}}$ between 4 and 4.6 GeV by the BESIII collaboration.

Source code:BESIII_2020_I1837725.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.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);

} ```