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BESIII_2017_I1644905

Cross section for $e^+e^-\to\phi\chi_{c(1,2)}$ at $\sqrt{s}=4.600$ GeV
Experiment: BESIII ()
Inspire ID: 1644905
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 97 (2018) 3, 032008
Beams: e+ e-
Beam energies: (2.3, 2.3) GeV
Run details:
  • e+ e- -> hadrons

Measurement of the cross section for $e^+e^-\to\phi\chi_{c(1,2)}$ at $\sqrt{s}=4.600$ GeV.

Source code: BESIII_2017_I1644905.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 chi_c(1,2)
 10  class BESIII_2017_I1644905 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1644905);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // projections
 23      declare(FinalState(), "FS");
 24      declare(UnstableParticles(), "UFS");
 25      for (unsigned int ix=0; ix<2; ++ix) {
 26        book(_h[ix], 1, 1, 1+ix);
 27      }
 28    }
 29
 30    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 31      for (const Particle &child : p.children()) {
 32        if (child.children().empty()) {
 33          --nRes[child.pid()];
 34          --ncount;
 35        }
 36        else {
 37          findChildren(child,nRes,ncount);
 38        }
 39      }
 40    }
 41
 42    /// Perform the per-event analysis
 43    void analyze(const Event& event) {
 44      const FinalState& fs = apply<FinalState>(event, "FS");
 45      map<long,int> nCount;
 46      int ntotal(0);
 47      for (const Particle& p: fs.particles()) {
 48        nCount[p.pid()] += 1;
 49        ++ntotal;
 50      }
 51      const FinalState& ufs = apply<FinalState>(event, "UFS");
 52      // loop over any phi mesons
 53      for (const Particle & phi : ufs.particles(Cuts::pid==333)) {
 54        bool matched = false;
 55        if (phi.children().empty()) continue;
 56        map<long,int> nRes = nCount;
 57        int ncount = ntotal;
 58        findChildren(phi,nRes,ncount);
 59        for (const Particle & chi : ufs.particles(Cuts::pid==20443 || Cuts::pid==445)) {
 60          if (chi.children().empty()) continue;
 61          map<long,int> nRes2 = nRes;
 62          int ncount2 = ncount;
 63          findChildren(chi,nRes2,ncount2);
 64          matched = true;
 65          for (const auto& val : nRes2) {
 66            if (val.second!=0) {
 67              matched = false;
 68              break;
 69            }
 70          }
 71          if(!matched) continue;
 72          if     (chi.pid()==20443) _h[0]->fill("4.6"s);
 73          else if(chi.pid()==  445) _h[1]->fill("4.6"s);
 74          break;
 75        }
 76        if(matched) break;
 77      }
 78    }
 79
 80
 81    /// Normalise histograms etc., after the run
 82    void finalize() {
 83      scale(_h, crossSection()/sumOfWeights()/picobarn);
 84    }
 85
 86    /// @}
 87
 88
 89    /// @name Histograms
 90    /// @{
 91    BinnedHistoPtr<string> _h[2];
 92    /// @}
 93
 94
 95  };
 96
 97
 98  RIVET_DECLARE_PLUGIN(BESIII_2017_I1644905);
 99
100}