Rivet analyses

title: BESII_2004_I661567

Cross sections for $e^+e^-\to\omega\pi^0$, $\rho\eta^{(\prime)}$ for $\sqrt{s}=3.65$, $3.686$, and $3.773$

Experiment: BESII (BEPC)

Inspire ID: 661567

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 70 (2004) 112007

Beams: e+ e-

Beam energies: (1.8, 1.8); (1.8, 1.8); (1.9, 1.9)GeV

Run details: - e+ e- > hadrons, pi0 and KS) set stable

The data were taken from Table III in the paper.

Source code:BESII_2004_I661567.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > omega pi0, rho eta(') class BESII_2004_I661567 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2004_I661567);


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

/// Book histograms and initialise projections before the run
void init() {
  // projection
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  // counter
  for (size_t ix = 0; ix < 3; ++ix) {
    book(_sigma[ix], 1, 1, 1 + ix);
  }

  for (const string& en : _sigma[0].binning().edges<0>()) {
    double eval = stod(en) * GeV;
    if (isCompatibleWithSqrtS(eval)) {
      _sqs = en;
      break;
    }
  }
  raiseBeamErrorIf(_sqs.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()];
      --ncount;
    }
    else {
      findChildren(child, nRes, ncount);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // final state particles
  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;
  }
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  // first the omega pi0 final state
  bool matched = false;
  for (const Particle& p : ufs.particles(Cuts::pid == 223)) {
    if (p.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p, nRes, ncount);
    if (ncount == 1) {
      matched = true;
      for (const auto& val : nRes) {
        if (val.first == 111) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        _sigma[0]->fill(_sqs);
        break;
      }
    }
  }
  if (matched) return;
  // rho eta states
  for (const Particle& p : ufs.particles(Cuts::pid == 113)) {
    if (p.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p, nRes, ncount);
    // check for eta/eta'
    for (const Particle& p2 : ufs.particles(Cuts::pid == 221 || Cuts::pid == 331)) {
      map<long, int> nResB = nRes;
      int ncountB = ncount;
      findChildren(p2, nResB, ncountB);
      if (ncountB != 0) continue;
      matched = true;
      for (const auto& val : nResB) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        if (p2.pid() == 221)
          _sigma[1]->fill(_sqs);
        else if (_sqs == "3.686")
          _sigma[2]->fill(_sqs);
        break;
      }
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _sigma[3];
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESII_2004_I661567);

} ```