Rivet analyses

title: SND_2003_I612867

Cross section for $e^+e^-\to\pi\gamma$ for energies between 600 MeV and 970 MeV

Experiment: SND (VEPP-2M)

Inspire ID: 612867

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys. Lett. B559, 171 (2003)

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons below 0.6 and 1.38 GeV

Cross section for $e^+e^-\to\pi\gamma$ for energies between 600 MeV and 970 MeV

Source code:SND_2003_I612867.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class SND_2003_I612867 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SND_2003_I612867);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(FinalState(), "FS");
  book(_numPi0Gamma, "TMP/Pi0Gamma");
}


/// 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();
}


/// Normalise histograms etc., after the run
void finalize() {

  double sigma = _numPi0Gamma->val();
  double error = _numPi0Gamma->err();
  sigma *= crossSection() / sumOfWeights() / nanobarn;
  error *= crossSection() / sumOfWeights() / nanobarn;
  Estimate1DPtr mult;
  book(mult, 1, 1, 1);
  for (auto& b : mult->bins()) {
    if (inRange(sqrtS() / MeV, b.xMin(), b.xMax())) {
      b.set(sigma, error);
    }
  }
}

/// @}


/// @name Histograms
/// @{
CounterPtr _numPi0Gamma;
/// @}

};

RIVET_DECLARE_PLUGIN(SND_2003_I612867);

} ```