Rivet analyses

title: BESIII_2023_I2685727

Cross section for $e^+e^-\to\phi+K^+K^-$ and $K^0_SK^0_S$ at energies between 3.773 and 4.7008 GeV

Experiment: BESIII (BEPC)

Inspire ID: 2685727

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 108 (2023) 3, 032004 - arXiv: 2304.07783

Beams: e+ e-

Beam energies: (1.9, 1.9); (1.9, 1.9); (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); (2.2, 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); (2.4, 2.4)GeV

Run details: - e+e- to hadrons, KS0 set stable

Cross section for $e^+e^-\to\phi+K^+K^-$ and $K^0_SK^0_S$ at energies between 3.773 and 4.7008 GeV.

Source code:BESIII_2023_I2685727.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e- > phi K+K-/KS0 KS0 class BESIII_2023_I2685727 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2685727);


/// @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(_nPhi[ix], 1, 1, 1 + ix);
  }
  for (const string& en : _nPhi[0].binning().edges<0>()) {
    const 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) {
  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");
  // find the phis
  for (const Particle& p : ufs.particles(Cuts::pid == 333)) {
    if (p.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p, nRes, ncount);
    // phi KK
    if (ncount != 2) continue;
    bool matched = false;
    for (unsigned int imode = 0; imode < 2; ++imode) {
      matched = true;
      for (const auto& val : nRes) {
        if (abs(val.first) == 310 && imode == 1) {
          if (val.second != 2) {
            matched = false;
            break;
          }
        }
        else if (abs(val.first) == 321 && imode == 0) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        _nPhi[imode]->fill(_sqs);
        break;
      }
    }
    if (matched) break;
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2023_I2685727);

} ```