Rivet analyses

title: SND_2001_I579319

Cross section for $e^+e^-2\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV

Experiment: SND (VEPP-2M)

Inspire ID: 579319

Status: VALIDATED

Authors: - Peter Richardson

References: - INP-2001-34 (2001)

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV

Source code:SND_2001_I579319.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class SND_2001_I579319 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SND_2001_I579319);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");

  // Book histograms
  for (size_t ix = 0; ix < 2; ++ix) {
    book(_npion[ix], 1 + ix, 1, 1);
    for (const string& en : _npion[ix].binning().edges<0>()) {
      const double eval = stod(en) * GeV;
      if (isCompatibleWithSqrtS(eval)) {
        _sqs[ix] = en;
        break;
      }
    }
  }
  raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].empty());
}


/// 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 != 4) vetoEvent;
  if (nCount[-211] == 2 && nCount[211] == 2) {
    _npion[0]->fill(_sqs[0]);
  }
  else if (nCount[-211] == 1 && nCount[211] == 1 && nCount[111] == 2) {
    _npion[1]->fill(_sqs[1]);
  }
}


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

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _npion[2];
string _sqs[2];
/// @}

};

RIVET_DECLARE_PLUGIN(SND_2001_I579319); } ```