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CMD3_2019_I1720610

Cross section for $e^+e^-\to3(\pi^+\pi^-)\pi^0$ below 2 GeV by CMD3
Experiment: CMD3 (VEPP-2M)
Inspire ID: 1720610
Status: VALIDATED
Authors:
  • Peter Richrdson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to3(\pi^+\pi^-)\pi^0$, and the resonant sub-processes $2(\pi^+\pi^-)\omega$ and $2(\pi^+\pi^-)\eta$, for energies below 2 GeV by the CMD3 experiment

Source code: CMD3_2019_I1720610.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 Add a short analysis description here
 10  class CMD3_2019_I1720610 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2019_I1720610);
 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
 27      // Book histograms
 28
 29      book(_c_all  , "/TMP/all");
 30      book(_c_omega, "/TMP/omega");
 31      book(_c_eta  , "/TMP/eta");
 32
 33    }
 34
 35    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 36      for(const Particle &child : p.children()) {
 37	if(child.children().empty()) {
 38	  --nRes[child.pid()];
 39	  --ncount;
 40	}
 41	else
 42	  findChildren(child,nRes,ncount);
 43      }
 44    }
 45
 46    /// Perform the per-event analysis
 47    void analyze(const Event& event) {
 48      // find the final-state particles
 49      const FinalState& fs = apply<FinalState>(event, "FS");
 50      map<long,int> nCount;
 51      int ntotal(0);
 52      for (const Particle& p : fs.particles()) {
 53	nCount[p.pid()] += 1;
 54	++ntotal;
 55      }
 56      if(ntotal==7 && nCount[211]==3 && nCount[-211]==3 && nCount[111] ==1 ) {
 57	_c_all->fill();
 58      }
 59      // find omega/phi + eta
 60      const FinalState& ufs = apply<FinalState>(event, "UFS");
 61      bool found=false;
 62      for (const Particle& p : ufs.particles()) {
 63	if(p.children().empty()) continue;
 64	// find the eta/omega
 65	if(p.pid()!=221 && p.pid()!=223) continue;
 66	map<long,int> nRes = nCount;
 67	int ncount = ntotal;
 68	findChildren(p,nRes,ncount);
 69	// eta/omega 2(pi+pi-)
 70	if(ncount==4) {
 71	  bool matched = true;
 72	  for(auto const & val : nRes) {
 73	    if(abs(val.first)==211 ) {
 74	      if(val.second !=2) {
 75		matched = false;
 76		break;
 77	      }
 78	    }
 79	    else if(val.second!=0) {
 80	      matched = false;
 81	      break;
 82	    }
 83	  }
 84	  if(matched) {
 85	    if(p.pid()==221)
 86	      _c_eta->fill();
 87	    else if(p.pid()==223)
 88	      _c_omega->fill();
 89	    found = true;
 90	    break;
 91	  }
 92	}
 93	if(found) break;
 94      }
 95
 96    }
 97
 98
 99    /// Normalise histograms etc., after the run
100    void finalize() {
101      double fact = crossSection()/nanobarn/sumOfWeights();
102      for (unsigned int ix=1;ix<4;++ix) {
103        double sigma(0.),error(0.);
104        if(ix==1) {
105          sigma = _c_all->val()*fact;
106          error = _c_all->err()*fact;
107        }
108        else if(ix==2) {
109          sigma = _c_eta->val()*fact;
110          error = _c_eta->err()*fact;
111        }
112        else if(ix==3) {
113          sigma = _c_omega->val()*fact;
114          error = _c_omega->err()*fact;
115        }
116        Estimate1DPtr  mult;
117        book(mult, 1, 1, ix);
118        for (auto& b : mult->bins()) {
119          if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
120            b.set(sigma, error);
121          }
122        }
123      }
124    }
125
126    /// @}
127
128
129    /// @name Histograms
130    /// @{
131    CounterPtr _c_all,_c_omega,_c_eta;
132    /// @}
133
134
135  };
136
137
138  RIVET_DECLARE_PLUGIN(CMD3_2019_I1720610);
139
140
141}