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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	Scatter2D temphisto(refData(1, 1, ix));
117	Scatter2DPtr  mult;
118	book(mult, 1, 1, ix);
119	for (size_t b = 0; b < temphisto.numPoints(); b++) {
120	  const double x  = temphisto.point(b).x();
121	  pair<double,double> ex = temphisto.point(b).xErrs();
122	  pair<double,double> ex2 = ex;
123	  if(ex2.first ==0.) ex2. first=0.0001;
124	  if(ex2.second==0.) ex2.second=0.0001;
125	  if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
126	    mult->addPoint(x, sigma, ex, make_pair(error,error));
127	  }
128	  else {
129	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
130	  }
131	}
132      }
133    }
134
135    //@}
136
137
138    /// @name Histograms
139    //@{
140    CounterPtr _c_all,_c_omega,_c_eta;
141    //@}
142
143
144  };
145
146
147  // The hook for the plugin system
148  RIVET_DECLARE_PLUGIN(CMD3_2019_I1720610);
149
150
151}