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BESIII_2022_I2614215

Cross section for $e^+e^-\to\omega X(3872)$ for $\sqrt{s}=4.661$ to 4.951 GeV
Experiment: BESIII (BEPC)
Inspire ID: 2614215
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: (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- > hadrons

Measurement of the cross section for $e^+e^-\to\omega X(3872)$ for $\sqrt{s}=4.661$ to 4.951 GeV by the BESIII collaboration. There is no consensus as to the nature of the $X(3872)$ $c\bar{c}$ state and therefore we taken its PDG code to be 9030443, i.e. the first unused code for an undetermined spin one $c\bar{c}$ state. This can be changed using the PID option if a different code is used by the event generator performing the simulation.

Source code: BESIII_2022_I2614215.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- > omega X(3872)
 10  class BESIII_2022_I2614215 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2614215);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // set the PDG code
 23      _pid = getOption<double>("PID", 9030443);
 24      // projections
 25      declare(FinalState(), "FS");
 26      declare(UnstableParticles(), "UFS");
 27      // counters
 28      book(_sigma,1,1,1);
 29      for(const string& en : _sigma.binning().edges<0>()) {
 30        const double end = std::stod(en)*GeV;
 31        if (isCompatibleWithSqrtS(end)) {
 32          _ecms = en;
 33          break;
 34        }
 35      }
 36      if (_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
 37    }
 38
 39    void findChildren(const Particle& p, map<long,int> & nRes, int &ncount) {
 40      for (const Particle &child : p.children()) {
 41        if (child.children().empty()) {
 42          --nRes[child.pid()];
 43          --ncount;
 44        }
 45        else {
 46          findChildren(child,nRes,ncount);
 47        }
 48      }
 49    }
 50
 51    /// Perform the per-event analysis
 52    void analyze(const Event& event) {
 53      const FinalState& fs = apply<FinalState>(event, "FS");
 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      for (const Particle& XX : ufs.particles(Cuts::pid==_pid)) {
 62      	if (XX.children().empty()) continue;
 63        bool matched = false;
 64       	map<long,int> nRes = nCount;
 65       	int ncount = ntotal;
 66       	findChildren(XX,nRes,ncount);
 67        for (const Particle & omega : ufs.particles(Cuts::pid==223)) {
 68          if (omega.parents()[0].pid()==_pid || omega.children().empty()) continue;
 69          map<long,int> nRes2 = nRes;
 70          int ncount2 = ncount;
 71          findChildren(omega,nRes2,ncount2);
 72          matched = true;
 73          for (const auto& val : nRes2) {
 74            if (val.second!=0) {
 75              matched = false;
 76              break;
 77            }
 78          }
 79          if(matched) {
 80            _sigma->fill(_ecms);
 81            break;
 82          }
 83        }
 84        if(matched) break;
 85      }
 86    }
 87
 88
 89    /// Normalise histograms etc., after the run
 90    void finalize() {
 91      scale(_sigma, crossSection()/ sumOfWeights() /picobarn);
 92    }
 93
 94    /// @}
 95
 96
 97    /// @name Histograms
 98    /// @{
 99    int _pid;
100    BinnedHistoPtr<string> _sigma;
101    string _ecms;
102    /// @}
103
104
105  };
106
107
108  RIVET_DECLARE_PLUGIN(BESIII_2022_I2614215);
109
110}