Rivet analyses

title: BESIII_2024_I2751879

Cross section for $e^+e^-\to\omega\chi_{c(1,2)}$ from $\sqrt{s}=4.308$ to 4.951 GeV

Experiment: BESIII (BEPC)

Inspire ID: 2751879

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2210.13058

Beams: e+ e-

Beam energies: (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.5, 2.5); (2.5, 2.5)GeV

Run details: - e+ e- -> hadrons

Measurement of the cross section for $e^+e^-\to\omega\chi_{c(1,2)}$ at from $\sqrt{s}=4.308$ to 4.951 GeV.

Source code:BESIII_2024_I2751879.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- -> omega chi_c(1,2) class BESIII_2024_I2751879 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2751879);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  for (size_t ix = 0; ix < 2; ++ix) {
    book(_sigma[ix], 1 + ix, 1, 1);
  }

  for (const string& en : _sigma[0].binning().edges<0>()) {
    double eval = stod(en);
    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) {
  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 FinalState& ufs = apply<FinalState>(event, "UFS");
  // loop over any phi mesons
  for (const Particle& phi : ufs.particles(Cuts::pid == 223)) {
    bool matched = false;
    if (phi.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(phi, nRes, ncount);
    for (const Particle& chi : ufs.particles(Cuts::pid == 20443 || Cuts::pid == 445)) {
      if (chi.children().empty()) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(chi, nRes2, ncount2);
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (!matched) continue;
      if (chi.pid() == 20443)
        _sigma[0]->fill(_sqs);
      else if (chi.pid() == 445)
        _sigma[1]->fill(_sqs);
      break;
    }
    if (matched) break;
  }
}


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

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _sigma[2];
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2024_I2751879);

} ```