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BESIII_2020_I1788734

Cross section for $e^+e^-\to \phi\eta^\prime$ for $\sqrt{s}$ between 3.05 and 3.08 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1788734
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
    No run details listed

Measurement of the cross section for $e^+e^-\to \phi\eta^\prime$ for $\sqrt{s}$ between 3.05 and 3.08 GeV by BESIII

Source code: BESIII_2020_I1788734.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_2020_I1788734 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1788734);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22
 23      // Initialise and register projections
 24      declare(FinalState(), "FS");
 25      declare(UnstableParticles(), "UFS");
 26      book(_nEtaPhi, "TMP/phietaprime");
 27    }
 28
 29    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 30      for (const Particle &child : p.children()) {
 31        if(child.children().empty()) {
 32          nRes[child.pid()]-=1;
 33          --ncount;
 34        }
 35        else
 36          findChildren(child,nRes,ncount);
 37      }
 38    }
 39
 40    /// Perform the per-event analysis
 41    void analyze(const Event& event) {
 42      const FinalState& fs = apply<FinalState>(event, "FS");
 43
 44      map<long,int> nCount;
 45      int ntotal(0);
 46      for (const Particle& p : fs.particles()) {
 47        nCount[p.pid()] += 1;
 48        ++ntotal;
 49      }
 50      const FinalState& ufs = apply<FinalState>(event, "UFS");
 51      for (const Particle& p : ufs.particles(Cuts::pid==PID::PHI)) {
 52        if(p.children().empty()) continue;
 53        map<long,int> nRes=nCount;
 54        int ncount = ntotal;
 55        findChildren(p,nRes,ncount);
 56        for (const Particle& p2 : ufs.particles(Cuts::pid==PID::ETAPRIME)) {
 57          if(p2.parents()[0].isSame(p)) continue;
 58          map<long,int> nResB = nRes;
 59          int ncountB = ncount;
 60          findChildren(p2,nResB,ncountB);
 61          if(ncountB!=0) continue;
 62          bool matched2 = true;
 63          for(auto const & val : nResB) {
 64            if(val.second!=0) {
 65              matched2 = false;
 66              break;
 67            }
 68          }
 69          if(matched2) {
 70            _nEtaPhi->fill();
 71          }
 72        }
 73      }
 74    }
 75
 76
 77    /// Normalise histograms etc., after the run
 78    void finalize() {
 79      double sigma = _nEtaPhi->val()*crossSection()/ sumOfWeights() /picobarn;
 80      double error = _nEtaPhi->err()*crossSection()/ sumOfWeights() /picobarn;
 81      Estimate1DPtr  mult;
 82      book(mult, 1, 1, 1);
 83      for (auto& b : mult->bins()) {
 84        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
 85          b.set(sigma, error);
 86        }
 87      }
 88    }
 89
 90    /// @}
 91
 92
 93    /// @name Histograms
 94    /// @{
 95    CounterPtr _nEtaPhi;
 96    /// @}
 97
 98  };
 99
100
101  RIVET_DECLARE_PLUGIN(BESIII_2020_I1788734);
102
103}