Rivet analyses

title: BESIII_2015_I1406939

Cross section for $e^+e^-\to \omega\chi_{c(1,2)}$ at energies between 4.42 and 4.6 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1406939

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D93 (2016) 011102, 2016

Beams: e+ e-

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

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to \omega\chi_{c(1,2)}$ at energies between 4.42 and 4.6 GeV by the BESIII collaboration.

Source code:BESIII_2015_I1406939.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Cross section for $e^+e^-\to \omega\chi_{c(1,2)}$ at energies between 4.42 and 4.6 GeV class BESIII_2015_I1406939 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2015_I1406939);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  for (size_t ix = 0; ix < 2; ++ix) {
    book(_nChi[ix], 2 + ix, 1, 6);
    for (const string& en : _nChi[ix].binning().edges<0>()) {
      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()];
      --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");
  bool matched = false;
  for (const Particle& p : ufs.particles(Cuts::pid == 20443 or Cuts::pid == 445)) {
    if (p.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p, nRes, ncount);
    for (const Particle& p2 : ufs.particles(Cuts::pid == 223)) {
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2, nRes2, ncount2);
      if (ncount2 != 0) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        if (p.pid() == 20443) {
          if (!_sqs[0].empty()) _nChi[0]->fill(_sqs[0]);
        }
        else if (p.pid() == 445) {
          if (!_sqs[1].empty()) _nChi[1]->fill(_sqs[1]);
        }
        break;
      }
    }
    if (matched) break;
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2015_I1406939);

} ```