Rivet analyses

Cross section for e⁺e⁻ → K⁺K⁻J/ψ and K_S⁰K_S⁰J/ψ for energies between 4.2 and 4.6 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1653121

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D97 (2018) 071101

Beams: e+ e-

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

Run details: - e+ e- to hadrons pi0 and KS0 set stable

Cross section for e⁺e⁻ → K⁺K⁻J/ψ and K_S⁰K_S⁰J/ψ for energies between 4.2 and 4.6 GeV measured by the BESIII collaboration.

Source code:`BESIII_2018_I1653121.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief e+e- > KK J/Psi
  class BESIII_2018_I1653121 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1653121);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::pid == 443), "UFS");
      book(_nKp, 1, 1, 1);
      book(_nK0, 1, 1, 2);
      for (const string& en : _nKp.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");
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        // J/psi KK
        if (ncount != 2) continue;
        bool matched = true;
        for (const auto& val : nRes) {
          if (abs(val.first) == 321 || abs(val.first) == 310) {
            continue;
          }
          else if (val.second != 0) {
            matched = false;
            break;
          }
        }
        if (matched) {
          if (nRes[321] == 1 && nRes[-321] == 1) {
            _nKp->fill(_sqs);
            break;
          }
          else if (nRes[310] == 2) {
            _nK0->fill(_sqs);
            break;
          }
        }
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      const double fact = crossSection() / sumOfWeights() / picobarn;
      scale(_nKp, fact);
      scale(_nK0, fact);
    }
    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _nKp, _nK0;
    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2018_I1653121);

}

Rivet analyses

Cross section for e+e− → K+K−J/ψ and KS0KS0J/ψ for energies between 4.2 and 4.6 GeV

Source code:BESIII_2018_I1653121.cc

Cross section for e⁺e⁻ → K⁺K⁻J/ψ and K_S⁰K_S⁰J/ψ for energies between 4.2 and 4.6 GeV

Source code:`BESIII_2018_I1653121.cc`