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BESIII_2020_I1817739

Cross section for $e^+e^-\to\omega\pi^0$ and $\omega\eta$ for centre-of-mass energies between 2.00 and 3.08 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1817739
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to\omega\pi^0$ and $\omega\eta$ for centre-of-mass energies between 2.00 and 3.08 GeV by the BESIII collaboration.

Source code: BESIII_2020_I1817739.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 pi0 and omega eta
 10  class BESIII_2020_I1817739 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1817739);
 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      book(_numOmegaPi, "TMP/OmegaPi");
 26      book(_nOmegaEta, "/TMP/nOmegaEta");
 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      map<long,int> nCount;
 44      int ntotal(0);
 45      for (const Particle& p : fs.particles()) {
 46        nCount[p.pid()] += 1;
 47        ++ntotal;
 48      }
 49      const FinalState& ufs = apply<FinalState>(event, "UFS");
 50      for (const Particle& p : ufs.particles(Cuts::pid==223)) {
 51        if(p.children().empty()) continue;
 52        map<long,int> nRes = nCount;
 53        int ncount = ntotal;
 54        findChildren(p,nRes,ncount);
 55        // check for omega pi0
 56        bool matched = true;
 57        for(auto const & val : nRes) {
 58          if(val.first==111) {
 59            if(val.second!=1) {
 60              matched = false;
 61              break;
 62            }
 63          }
 64          else if(val.second!=0) {
 65            matched = false;
 66            break;
 67          }
 68        }
 69        if(matched) {
 70          _numOmegaPi->fill();
 71          break;
 72        }
 73        // now for omega eta
 74        for (const Particle& p2 : ufs.particles(Cuts::pid==221)) {
 75          map<long,int> nResB = nRes;
 76          int ncountB = ncount;
 77          findChildren(p2,nResB,ncountB);
 78          if(ncountB!=0) continue;
 79          matched = true;
 80          for(auto const & val : nResB) {
 81            if(val.second!=0) {
 82              matched = false;
 83              break;
 84            }
 85          }
 86          if(matched) {
 87            _nOmegaEta->fill();
 88            break;
 89          }
 90        }
 91        if(matched) break;
 92      }
 93    }
 94
 95
 96    /// Normalise histograms etc., after the run
 97    void finalize() {
 98      for(unsigned int ix=1;ix<3;++ix) {
 99        double sigma,error;
100        if(ix==1) {
101          sigma = _nOmegaEta->val();
102          error = _nOmegaEta->err();
103        }
104        else {
105          sigma = _numOmegaPi->val();
106          error = _numOmegaPi->err();
107        }
108        sigma *= crossSection()/ sumOfWeights() /picobarn;
109        error *= crossSection()/ sumOfWeights() /picobarn;
110        Estimate1DPtr mult;
111        book(mult, ix, 1, 1);
112        for (auto& b : mult->bins()) {
113          if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
114            b.set(sigma, error);
115          }
116        }
117      }
118    }
119
120    /// @}
121
122
123    /// @name Histograms
124    /// @{
125    CounterPtr _nOmegaEta;
126    CounterPtr _numOmegaPi;
127    /// @}
128
129  };
130
131
132  RIVET_DECLARE_PLUGIN(BESIII_2020_I1817739);
133
134}