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Rivet analyses reference

BESIII_2018_I1653121

Cross section for $e^+e^-\to K^+K^-J/\psi$ and $K^0_SK^0_SJ/\psi$ 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 $e^+e^-\to K^+K^-J/\psi$ and $K^0_SK^0_SJ/\psi$ for energies between 4.2 and 4.6 GeV measured by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: BESIII_2018_I1653121.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief e+e- > KK J/Psi
 10  class BESIII_2018_I1653121 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1653121);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      declare(FinalState(), "FS");
 23      declare(UnstableParticles(Cuts::pid==443), "UFS");
 24      book(_nKp, 1, 1, 1);
 25      book(_nK0, 1, 1, 2);
 26      for (const string& en : _nKp.binning().edges<0>()) {
 27        const double end = std::stod(en)*GeV;
 28        if (isCompatibleWithSqrtS(end)) {
 29          _ecms = en;
 30          break;
 31        }
 32      }
 33      if (_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
 34    }
 35
 36    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 37      for (const Particle &child : p.children()) {
 38        if(child.children().empty()) {
 39          --nRes[child.pid()];
 40          --ncount;
 41        }
 42        else
 43          findChildren(child,nRes,ncount);
 44      }
 45    }
 46
 47    /// Perform the per-event analysis
 48    void analyze(const Event& event) {
 49      const FinalState& fs = apply<FinalState>(event, "FS");
 50      map<long,int> nCount;
 51      int ntotal(0);
 52      for (const Particle& p : fs.particles()) {
 53        nCount[p.pid()] += 1;
 54        ++ntotal;
 55      }
 56      const FinalState& ufs = apply<FinalState>(event, "UFS");
 57      for (const Particle& p : ufs.particles()) {
 58        if(p.children().empty()) continue;
 59        map<long,int> nRes = nCount;
 60        int ncount = ntotal;
 61        findChildren(p,nRes,ncount);
 62        // J/psi KK
 63        if(ncount!=2) continue;
 64        bool matched = true;
 65        for(auto const & val : nRes) {
 66          if(abs(val.first)==321 || abs(val.first)==310) {
 67            continue;
 68          }
 69          else if(val.second!=0) {
 70            matched = false;
 71            break;
 72          }
 73        }
 74        if(matched) {
 75          if(nRes[321]==1 && nRes[-321]==1) {
 76            _nKp->fill(_ecms);
 77            break;
 78          }
 79          else if(nRes[310]==2) {
 80            _nK0->fill(_ecms);
 81            break;
 82          }
 83        }
 84      }
 85    }
 86
 87    /// Normalise histograms etc., after the run
 88    void finalize() {
 89      const double fact = crossSection()/ sumOfWeights() /picobarn;
 90      scale(_nKp,fact);
 91      scale(_nK0,fact);
 92    }
 93    /// @}
 94
 95
 96    /// @name Histograms
 97    /// @{
 98    BinnedHistoPtr<string> _nKp, _nK0;
 99    string _ecms;
100    /// @}
101
102
103  };
104
105
106  RIVET_DECLARE_PLUGIN(BESIII_2018_I1653121);
107
108}