Rivet analyses

title: CMD3_2019_I1770428

$e^+e^-\to K^0_SK^0_S\pi^+\pi^-$ below 2 GeV

Experiment: CMD3 (VEPP-2M)

Inspire ID: 1770428

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1912.05751

Beams: e- e+

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to K^0_SK^0_S\pi^+\pi^-$ below 2 GeV by the CMD3 experiment

Source code:CMD3_2019_I1770428.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief CMD3 K0 K0 pi+pi- class CMD3_2019_I1770428 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2019_I1770428);


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

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

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

  // Book histograms
  book(_cK0K0pippim, "TMP/K0K0pippim", refData(1, 1, 6));
  book(_h_pipi, 2, 1, 1);
  book(_h_total, 2, 1, 2);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");

  map<long, int> nCount;
  int ntotal(0);
  Particles pip, k0;
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    if (p.abspid() == 211)
      pip.push_back(p);
    else if (p.pid() == 310)
      k0.push_back(p);
    ++ntotal;
  }
  if (ntotal == 4 && nCount[310] == 2 && nCount[211] == 1 && nCount[-211] == 1) {
    _cK0K0pippim->fill(sqrtS() / MeV);
    FourMomentum ppipi = pip[0].momentum() + pip[1].momentum();
    _h_pipi->fill(ppipi.mass() / MeV);
    for (unsigned int ix = 0; ix < 2; ++ix) _h_total->fill((ppipi + k0[ix].momentum()).mass() / MeV);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_pipi);
  normalize(_h_total);
  scale(_cK0K0pippim, crossSection() / sumOfWeights() / nanobarn);
  Estimate1DPtr mult;
  book(mult, 1, 1, 6);
  barchart(_cK0K0pippim, mult);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _cK0K0pippim;
Histo1DPtr _h_pipi, _h_total;
/// @}

};

RIVET_DECLARE_PLUGIN(CMD3_2019_I1770428);

} ```