Rivet analyses

title: BESII_2005_I685906

Cross section for $e^+e^-\to$ proton and antiproton between 2 and 3.07 GeV

Experiment: BESII (BEPC)

Inspire ID: 685906

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D91 (2015) 112004, 2015

Beams: e+ e-

Beam energies: (1.0, 1.0); (1.1, 1.1); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3); (1.4, 1.4); (1.4, 1.4); (1.5, 1.5); (1.5, 1.5)GeV

Run details: - e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to p\bar{p}$ for energies between 2 and 3.07 GeV.

Source code:BESII_2005_I685906.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Cross section for e+e- to proton and antiproton between 2 and 3.07 GeV class BESII_2005_I685906 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2005_I685906);


/// @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 = std::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() != 2) 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() / picobarn);
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESII_2005_I685906);

} ```