Rivet analyses

title: CMD2_1995_I406880

Cross section for $e^+e^-\to$ $K^+K^-$, $K_S^0K_L^0$, $\pi^+\pi^-\pi^0$ and $\eta\gamma$ near the $\phi$ resonance

Experiment: CMD2 (VEPP-2M)

Inspire ID: 406880

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B364 (1995) 199-206, 1995

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Source code:CMD2_1995_I406880.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e- -> hadrons near phi class CMD2_1995_I406880 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_1995_I406880);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  book(_nKpKm, "TMP/KpKm", refData(1, 1, 1));
  book(_nK0K0, "TMP/K0K0", refData(1, 1, 2));
  book(_n3pi, "TMP/3pi", refData(1, 1, 3));
  book(_numEtaGamma, "TMP/EtaGamma", refData(1, 1, 4));
}

void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) {
  for (const Particle& child : p.children()) {
    if (child.children().empty()) {
      --nRes[child.pid()];
      --ncount;
    }
    else
      findChildren(child, nRes, ncount);
  }
}

/// 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) {
    if (nCount[321] == 1 && nCount[-321] == 1)
      _nKpKm->fill(sqrtS() / MeV);
    else if (nCount[130] == 1 && nCount[310] == 1)
      _nK0K0->fill(sqrtS() / MeV);
  }
  else if (ntotal == 3 && nCount[211] == 1 && nCount[-211] == 1 && nCount[111] == 1)
    _n3pi->fill(sqrtS() / MeV);

  const FinalState& ufs = apply<FinalState>(event, "UFS");
  for (const Particle& p : ufs.particles()) {
    if (p.children().empty()) continue;
    // find the omega
    if (p.pid() == 221) {
      map<long, int> nRes = nCount;
      int ncount = ntotal;
      findChildren(p, nRes, ncount);
      // eta pi+pi-
      if (ncount != 1) continue;
      bool matched = true;
      for (const auto& val : nRes) {
        if (val.first == 22) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) _numEtaGamma->fill(sqrtS() / MeV);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / sumOfWeights() / nanobarn;
  Estimate1DPtr mult;
  scale(_nKpKm, fact);
  book(mult, 1, 1, 1);
  barchart(_nKpKm, mult);
  scale(_nK0K0, fact);
  book(mult, 1, 1, 2);
  barchart(_nK0K0, mult);
  scale(_n3pi, fact);
  book(mult, 1, 1, 3);
  barchart(_n3pi, mult);
  scale(_numEtaGamma, fact);
  book(mult, 1, 1, 4);
  barchart(_numEtaGamma, mult);
}
/// @}


/// @name Histograms
/// @{
Histo1DPtr _nKpKm, _nK0K0, _n3pi, _numEtaGamma;
/// @}

};

RIVET_DECLARE_PLUGIN(CMD2_1995_I406880);

} ```