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BABAR_2021_I1938254

Cross sections for $e^+e^-\to\pi^+\pi^-4\pi^0$ and $e^+e^-\to\pi^+\pi^-3\pi^0\eta$ between threshold and 4.5 GeV
Experiment: BABAR (PEP-II)
Inspire ID: 1938254
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • 2110.00823
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Cross sections for $e^+e^-\to\pi^+\pi^-4\pi^0$ and $e^+e^-\to\pi^+\pi^-3\pi^0\eta$ between threshold and 4.5 GeV measured by BaBar using radiative return. The contributions of the $\eta\pi^+\pi^-\pi^0$, $\eta\omega$, $\omega\pi^0\pi^0\pi^0$ intermediate states are also measured. Useful to compare hadronization and other non-perturbative models at low energies between 1.4 and 4.5 GeV.

Source code: BABAR_2021_I1938254.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- > pi+pi-4pi0 and pi+pi-3pi0 eta
 10  class BABAR_2021_I1938254 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2021_I1938254);
 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      // Histograms
 26      for(unsigned int ix=0;ix<5;++ix) {
 27	book(_num[ix],"TMP/num_"+to_string(ix));
 28      }
 29    }
 30
 31    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 32      for( const Particle &child : p.children()) {
 33	if(child.children().empty()) {
 34	  --nRes[child.pid()];
 35	  --ncount;
 36	}
 37	else
 38	  findChildren(child,nRes,ncount);
 39      }
 40    }
 41
 42    /// Perform the per-event analysis
 43    void analyze(const Event& event) {
 44      const FinalState& fs = apply<FinalState>(event, "FS");
 45
 46      map<long,int> nCount;
 47      int ntotal(0);
 48      for (const Particle& p : fs.particles()) {
 49	nCount[p.pid()] += 1;
 50	++ntotal;
 51      }
 52      // stable final state
 53      if(nCount[211]==1 && nCount[-211]==1 && nCount[111]==4)
 54	_num[0]->fill();
 55      // intermediate states
 56      const FinalState& ufs = apply<FinalState>(event, "UFS");
 57      for (const Particle& p : ufs.particles(Cuts::pid==221 || Cuts::pid==223)) {
 58	map<long,int> nRes = nCount;
 59	int ncount = ntotal;
 60	findChildren(p,nRes,ncount);
 61	// eta +X
 62	int idOther;
 63	if(p.pid()==221) {
 64	  idOther=223;
 65	  bool matched = true;
 66	  for(auto const & val : nRes) {
 67	    if(abs(val.first)==211 || val.first==-211 ) {
 68	      if(val.second !=1) {
 69		matched = false;
 70		break;
 71	      }
 72	    }
 73	    else if(val.first==111) {
 74	      // 1 or 3 pi0
 75	      if(val.second !=3 && val.second != 1) {
 76		matched = false;
 77		break;
 78	      }
 79	    }
 80	    else if(val.second!=0) {
 81	      matched = false;
 82	      break;
 83	    }
 84	  }
 85	  if(matched) {
 86	    if(nRes[111]==1)
 87	      _num[1]->fill();
 88	    else
 89	      _num[4]->fill();
 90	  }
 91
 92
 93	}
 94	// omega+X
 95	else {
 96	  idOther=221;
 97	  // omega+ 3pi0
 98	  bool matched = true;
 99	  for(auto const & val : nRes) {
100	    if(abs(val.first)==111) {
101	      if(val.second !=3) {
102		matched = false;
103		break;
104	      }
105	    }
106	    else if(val.second!=0) {
107	      matched = false;
108	      break;
109	    }
110	  }
111	  if(matched) {
112	    _num[3]->fill();
113	  }
114	}
115	for (const Particle& p2 : ufs.particles(Cuts::pid==idOther)) {
116	  map<long,int> nResB = nRes;
117	  int ncountB = ncount;
118	  findChildren(p2,nResB,ncountB);
119	  if(ncountB!=0) continue;
120	  bool matched2 = true;
121	  for(auto const & val : nResB) {
122	    if(val.second!=0) {
123	      matched2 = false;
124	      break;
125	    }
126	  }
127	  if(matched2) {
128	    _num[2]->fill();
129	  }
130	}
131      }
132    }
133
134
135    /// Normalise histograms etc., after the run
136    void finalize() {
137      double fact = crossSection()/nanobarn/sumOfWeights();
138      for (unsigned int ix=0;ix<5;++ix) {
139        double sigma = _num[ix]->val()*fact;
140        double error = _num[ix]->err()*fact;
141        Estimate1DPtr  mult;
142        book(mult, 1+ix, 1, 1);
143        for (auto& b : mult->bins()) {
144          if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
145            b.set(sigma, error);
146          }
147        }
148      }
149    }
150
151    ///@}
152
153
154    /// @name Histograms
155    ///@{
156    CounterPtr _num[5];
157    ///@}
158
159
160  };
161
162
163  RIVET_DECLARE_PLUGIN(BABAR_2021_I1938254);
164
165}