Rivet analyses

title: FENICE_1998_I471263

Cross section for $e^+e^-\to n\bar{n}$ between 1.9 and 2.44 GeV

Experiment: FENICE (ADONE)

Inspire ID: 471263

Status: VALIDATED

Authors: - Peter Richardson

References: - Nucl.Phys. B517 (1998) 3-35, 1998

Beams: e+ e-

Beam energies: (0.9, 0.9); (1.0, 1.0); (1.0, 1.0); (1.1, 1.1); (1.2, 1.2)GeV

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to n\bar{n}$ between 1.9 and 2.44 GeV.

Source code:FENICE_1998_I471263.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e-> n nbar class FENICE_1998_I471263 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(FENICE_1998_I471263);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  book(_nNeutron, 1, 1, 1);
  for (const string& en : _nNeutron.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");
  // total hadronic and muonic cross sections
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    ++nCount[p.pid()];
    ++ntotal;
  }
  if (ntotal == 2 && nCount[2112] == 1 && nCount[-2112] == 1) _nNeutron->fill(_sqs);
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(FENICE_1998_I471263);

} ```