Rivet analyses

title: CMD2_2004_I630009

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

Experiment: CMD2 (VEPP-2M)

Inspire ID: 630009

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B580 (2004) 119-128, 2004

Beams: e+ e-

Beam energies: (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5)GeV

Run details: - e+e- to hadrons

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

Source code:CMD2_2004_I630009.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class CMD2_2004_I630009 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2004_I630009);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  book(_numPiPiGamma, 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(round(sqrtS() / MeV));
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(CMD2_2004_I630009);

} ```