Rivet analyses

title: SND_2002_I587084

Cross section for $e^+e^-\to\pi^0\pi^0\gamma$ at energies between 0.6 and 0.97 GeV.

Experiment: SND (VEPP-2M)

Inspire ID: 587084

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D94 (2016) no.11, 112001

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Source code:SND_2002_I587084.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class SND_2002_I587084 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SND_2002_I587084);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  book(_numPiPiGamma, "TMP/PiPiGamma", refData(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;
  }
  // three particles (pi0 pi0 gamma)
  if (ntotal != 3) vetoEvent;
  if (nCount[111] == 2 && nCount[22] == 1) _numPiPiGamma->fill(sqrtS() / MeV);
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_numPiPiGamma, crossSection() / sumOfWeights() / nanobarn);
  Estimate1DPtr mult;
  book(mult, 1, 1, 1);
  barchart(_numPiPiGamma, mult);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _numPiPiGamma;
/// @}

};

RIVET_DECLARE_PLUGIN(SND_2002_I587084);

} ```