Rivet analyses

title: ARGUS_1987_I247567

Cross Section for $\gamma\gamma\to 2\pi^+2\pi^-\pi^0$ and $\rho^0\omega$ for $\sqrt{s}=1\to3.3\,$GeV

Experiment: ARGUS (DORIS)

Inspire ID: 247567

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B 196 (1987) 101

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons

Measurement of the cross section for $\gamma\gamma\to 2\pi^+2\pi^-\pi^0$ and $\rho^0\omega$ for $\sqrt{s}=1\to3.3\,$GeV

Source code:ARGUS_1987_I247567.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief cross section for e+e- -> 2pi+ 2pi- pi0 and rho0 omega class ARGUS_1987_I247567 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I247567);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(Cuts::pid == 113 || Cuts::pid == 223), "UFS");
  // histos
  for (size_t ix = 0; ix < 2; ++ix) {
    book(_c[ix], 1 + ix, 1, 1);
    for (const string& en : _c[ix].binning().edges<0>()) {
      const size_t idx = en.find("-");
      if (idx != std::string::npos) {
        const double emin = std::stod(en.substr(0, idx));
        const double emax = stod(en.substr(idx + 1, string::npos));
        if (inRange(sqrtS() / GeV, emin, emax)) {
          _sqs[ix] = en;
          break;
        }
      }
      else {
        const double eval = stod(en) * GeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs[ix] = en;
          break;
        }
      }
    }
  }
  raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].empty());
}

void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) const {
  for (const Particle& child : p.children()) {
    if (child.children().empty()) {
      nRes[child.pid()] -= 1;
      --ncount;
    }
    else {
      findChildren(child, nRes, ncount);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  // find the final-state particles
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  if (ntotal == 5 && nCount[211] == 2 && nCount[-211] == 2 && nCount[111] == 1) _c[0]->fill(_sqs[0]);
  // rho0 mesons
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& rho : ufs.particles(Cuts::pid == 113)) {
    if (rho.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(rho, nRes, ncount);
    bool matched = false;
    // omega
    for (const Particle& omega : ufs.particles(Cuts::pid == 223)) {
      if (omega.children().empty()) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(omega, nRes2, ncount2);
      if (ncount2 != 0) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        _c[1]->fill(_sqs[1]);
        break;
      }
    }
    if (matched) break;
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(ARGUS_1987_I247567);

} ```