Rivet analyses

title: BESIII_2018_I1685535

Cross section for $e^+e^-\to\pi^+D^0D^{*-}$ +c.c. cross section between 4.05 and 4.60 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1685535

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 122 (2019) no.10, 102002

Beams: e+ e-

Beam energies: (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (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); (2.2, 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, 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); (2.3, 2.3)GeV

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+D^0D^{*-}$ +c.c. cross section between 4.05 and 4.60 GeV by the BES collaboration.

Source code:BESIII_2018_I1685535.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Cross section for D0 D*- pi+ +c.c class BESIII_2018_I1685535 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1685535);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  // Book histograms
  for (size_t ix = 0; ix < 2; ++ix) {
    book(_nD0[ix], 1 + ix, 1, 1);
    for (const string& en : _nD0[ix].binning().edges<0>()) {
      const double end = stod(en) * GeV;
      if (isCompatibleWithSqrtS(end)) {
        _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");

  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");


  for (size_t ix = 0; ix < ufs.particles().size(); ++ix) {
    const Particle& p1 = ufs.particles()[ix];
    if (p1.abspid() != 421) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    bool matched = false;
    int id2 = p1.pid() > 0 ? -413 : 413;
    int ipi = p1.pid() > 0 ? 211 : -211;
    for (size_t iy = 0; iy < ufs.particles().size(); ++iy) {
      if (ix == iy) continue;
      const Particle& p2 = ufs.particles()[iy];
      if (p2.pid() != id2) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2, nRes2, ncount2);
      if (ncount2 != 1) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.first == ipi) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) break;
    }
    if (matched) {
      for (size_t ix = 0; ix < 2; ++ix) {
        if (!_sqs[ix].empty()) _nD0[ix]->fill(_sqs[ix]);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_nD0, crossSection() / sumOfWeights() / nanobarn);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _nD0[2];
string _sqs[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2018_I1685535);

} ```