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BESIII_2023_I2705058

Cross section for $e^+e^-\to\eta^\prime\phi$ for centre-of-mass energies between 3.508 to 4.951 GeV
Experiment: BESIII (BEPC)
Inspire ID: 2705058
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.8, 1.8); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (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); (2.2, 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); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.5, 2.5); (2.5, 2.5) GeV
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to\eta^\prime\phi$ for centre-of-mass energies between 3.508 to 4.951 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: BESIII_2023_I2705058.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- > phi eta'
 10  class BESIII_2023_I2705058 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2705058);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // Initialise and register projections
 23      declare(FinalState(), "FS");
 24      declare(UnstableParticles(), "UFS");
 25      for(unsigned int ix=0;ix<2;++ix)
 26	book(_sigma[ix],1,1,1+ix);
 27
 28      for (const string& en : _sigma[0].binning().edges<0>()) {
 29        double end = std::stod(en)*GeV;
 30        if(isCompatibleWithSqrtS(end)) {
 31          _ecms = en;
 32          break;
 33        }
 34      }
 35      if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
 36    }
 37
 38    void findChildren(const Particle& p, map<long,int>& nRes, int &ncount) {
 39      for (const Particle& child : p.children()) {
 40        if (child.children().empty()) {
 41          nRes[child.pid()]-=1;
 42          --ncount;
 43        }
 44        else {
 45          findChildren(child,nRes,ncount);
 46        }
 47      }
 48    }
 49
 50    /// Perform the per-event analysis
 51    void analyze(const Event& event) {
 52      const FinalState& fs = apply<FinalState>(event, "FS");
 53
 54      map<long,int> nCount;
 55      int ntotal(0);
 56      for (const Particle& p : fs.particles()) {
 57        nCount[p.pid()] += 1;
 58        ++ntotal;
 59      }
 60      const FinalState& ufs = apply<FinalState>(event, "UFS");
 61
 62      // loop over eta mesons
 63      for (const Particle& p : ufs.particles(Cuts::pid==331)) {
 64        if (p.children().empty()) continue;
 65        map<long,int> nRes = nCount;
 66        int ncount = ntotal;
 67        findChildren(p,nRes,ncount);
 68        // loop over phi mesons
 69        for (const Particle& p2 : ufs.particles(Cuts::pid==333)) {
 70          if (p2.parents()[0].isSame(p)) continue;
 71          map<long,int> nResB = nRes;
 72          int ncountB = ncount;
 73          findChildren(p2,nResB,ncountB);
 74          bool born    = true;
 75          bool matched = true;
 76          for (const auto& val : nResB) {
 77            if (val.first==22) {
 78              if (val.second!=ncountB) {
 79                matched = false;
 80                break;
 81              }
 82              if (val.second!=0) born=false;
 83            }
 84            if (val.second!=0) {
 85              matched = false;
 86              break;
 87            }
 88          }
 89          if (matched) {
 90	    _sigma[0]->fill(_ecms);
 91	    if(born) _sigma[1]->fill(_ecms);
 92          }
 93        }
 94      }
 95    }
 96
 97
 98    /// Normalise histograms etc., after the run
 99    void finalize() {
100      double fact = crossSection()/ sumOfWeights()/picobarn;
101      for(unsigned int ix=0;ix<2;++ix) {
102	scale(_sigma[ix],fact);
103      }
104    }
105
106    /// @}
107
108
109    /// @name Histograms
110    /// @{
111    BinnedHistoPtr<string> _sigma[2];
112    string _ecms;
113    /// @}
114
115
116  };
117
118
119  RIVET_DECLARE_PLUGIN(BESIII_2023_I2705058);
120
121}