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CMD3_2017_I1606078

Cross section for $e^+e^-\to\pi^+\pi^-\pi^0\eta$ for energies below 2 GeV
Experiment: CMD3 (VEPP-2M)
Inspire ID: 1606078
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+\pi^-\pi^0\eta$, and the resonant sub-processes $\omega\eta$and $a_0(980)\rho$, for energies below 2 GeV by the CMD3 experiment

Source code: CMD3_2017_I1606078.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 CMD3 pi+pi-pi0eta cross section
 10  class CMD3_2017_I1606078 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2017_I1606078);
 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
 28      book(_c_all  , "/TMP/all");
 29      book(_c_omega, "/TMP/omega");
 30      book(_c_rho  , "/TMP/rho");
 31      book(_c_other, "/TMP/other");
 32    }
 33
 34    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 35      for(const Particle &child : p.children()) {
 36	if(child.children().empty()) {
 37	  --nRes[child.pid()];
 38	  --ncount;
 39	}
 40	else
 41	  findChildren(child,nRes,ncount);
 42      }
 43    }
 44
 45    /// Perform the per-event analysis
 46    void analyze(const Event& event) {
 47      // find the final-state particles
 48      const FinalState& fs = apply<FinalState>(event, "FS");
 49      map<long,int> nCount;
 50      int ntotal(0);
 51      for (const Particle& p : fs.particles()) {
 52	nCount[p.pid()] += 1;
 53	++ntotal;
 54      }
 55      // find omega/phi + eta 
 56      const FinalState& ufs = apply<FinalState>(event, "UFS");
 57      bool found = false, foundOmegaPhi = false;
 58      for (const Particle& p : ufs.particles()) {
 59	if(p.children().empty()) continue;
 60	// find the eta
 61	if(p.pid()!=221) continue;
 62	map<long,int> nRes = nCount;
 63	int ncount = ntotal;
 64	findChildren(p,nRes,ncount);
 65	// eta pi+pi-pi0
 66	if(ncount==3) {
 67	  bool matched = true;
 68	  for(auto const & val : nRes) {
 69	    if(abs(val.first)==211 || val.first==111 ) {
 70	      if(val.second !=1) {
 71		matched = false;
 72		break;
 73	      }
 74	    }
 75	    else if(val.second!=0) {
 76	      matched = false;
 77	      break;
 78	    }
 79	  }
 80	  if(matched) {
 81	    _c_all->fill();
 82	    found = true;
 83	  }
 84	}
 85	for (const Particle& p2 : ufs.particles()) {
 86	  if(p2.pid()!=223 && p2.pid()!=333) continue;
 87	  map<long,int> nResB = nRes;
 88	  int ncountB = ncount;
 89	  findChildren(p2,nResB,ncountB);
 90	  if(ncountB!=0) continue;
 91	  bool matched2 = true;
 92	  for(auto const & val : nResB) {
 93	    if(val.second!=0) {
 94	      matched2 = false;
 95	      break;
 96	    }
 97	  }
 98	  if(matched2) {
 99	    if(p2.pid()==223)
100	      _c_omega->fill();
101	    foundOmegaPhi=true;
102	  }
103	}
104      }
105      // find a_0 rho
106      bool founda0Rho=false;
107      for (const Particle& p : ufs.particles()) {
108      	if(p.children().empty()) continue;
109	// find the rho
110	if(p.pid()!=113 && abs(p.pid())!=213)
111	  continue;
112        map<long,int> nRes = nCount;
113        int ncount = ntotal;
114        findChildren(p,nRes,ncount);
115	int a1id(0);
116	if(p.pid()==213)
117	  a1id = 9000211;
118	else if(p.pid()==-213)
119	  a1id =-9000211;
120	else
121	  a1id = 9000111;
122	for (const Particle& p2 : ufs.particles()) {
123	  if(p2.pid()!=a1id) continue;
124	  map<long,int> nResB = nRes;
125	  int ncountB = ncount;
126	  findChildren(p2,nResB,ncountB);
127	  if(ncountB!=0) continue;
128	  bool matched = true;
129	  for(auto const & val : nResB) {
130	    if(val.second!=0) {
131	      matched = false;
132	      break;
133	    }
134	  }
135	  if(matched) {
136	    _c_rho->fill();
137	    founda0Rho=true;
138	    break;
139	  }
140	}
141	if(founda0Rho) break;
142      }
143      if(found && !foundOmegaPhi && ! founda0Rho)
144	_c_other->fill();
145    }
146
147
148    /// Normalise histograms etc., after the run
149    void finalize() {
150      double fact = crossSection()/nanobarn/sumOfWeights();
151      for(unsigned int ix=1;ix<5;++ix) {
152	double sigma(0.),error(0.);
153	if(ix==1) {
154	  sigma = _c_all->val()*fact;
155	  error = _c_all->err()*fact;
156	}
157	else if(ix==2) {
158	  sigma = _c_omega->val()*fact;
159	  error = _c_omega->err()*fact;
160	}
161	else if(ix==3) {
162	  sigma = _c_rho->val()*fact;
163	  error = _c_rho->err()*fact;
164	}
165	else if(ix==4) {
166	  sigma = _c_other->val()*fact;
167	  error = _c_other->err()*fact;
168	}
169	Scatter2D temphisto(refData(1, 1, ix));
170	Scatter2DPtr  mult;
171	book(mult, 1, 1, ix);
172	for (size_t b = 0; b < temphisto.numPoints(); b++) {
173	  const double x  = temphisto.point(b).x();
174	  pair<double,double> ex = temphisto.point(b).xErrs();
175	  pair<double,double> ex2 = ex;
176	  if(ex2.first ==0.) ex2. first=0.0001;
177	  if(ex2.second==0.) ex2.second=0.0001;
178	  if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
179	    mult->addPoint(x, sigma, ex, make_pair(error,error));
180	  }
181	  else {
182	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
183	  }
184	}
185      }
186    }
187
188    //@}
189
190
191    /// @name Histograms
192    //@{
193    CounterPtr _c_all, _c_omega, _c_rho, _c_other;
194    //@}
195
196
197  };
198
199
200  // The hook for the plugin system
201  RIVET_DECLARE_PLUGIN(CMD3_2017_I1606078);
202
203
204}