Rivet analyses

title: SND_2018_I1694988

Cross section for $e^+e^-\to\pi\gamma$ for energies between 1.075 GeV and 2 GeV

Experiment: SND (VEPP-2M)

Inspire ID: 1694988

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1809.07631

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons

Cross section for $e^+e^-\to\pi\gamma$ for energies between 1.075 GeV and 2 GeV

Source code:SND_2018_I1694988.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief e+e- -> pi0 gamma class SND_2018_I1694988 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SND_2018_I1694988);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(FinalState(), "FS");
  book(_numPi0Gamma, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  const FinalState& fs = apply<FinalState>(event, "FS");

  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  if (ntotal == 2 && nCount[22] == 1 && nCount[111] == 1) _numPi0Gamma->fill(round(sqrtS() / MeV));
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_numPi0Gamma, crossSection() / sumOfWeights() / picobarn);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<int> _numPi0Gamma;
/// @}

};

RIVET_DECLARE_PLUGIN(SND_2018_I1694988);

} ```