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SND_2020_I1809286

Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ between 1.15 and 2 GeV
Experiment: SND (VEPP-2000)
Inspire ID: 1809286
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ between 1.15 and 2 GeV measured by SND. The $\omega\pi^0$, $\rho\pi$ and $\rho(1450)\pi$ subprocesses are also extracted.

Source code: SND_2020_I1809286.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-pi0
 10  class SND_2020_I1809286 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1809286);
 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(_c_total, "/TMP/total");
 26      book(_c_omega, "/TMP/omega");
 27      book(_c_rho  , "/TMP/rho"  );
 28      book(_c_rhop , "/TMP/rhop" );
 29      if(inRange(sqrtS()/GeV,1.42,1.48)) {
 30	book(_h_x,4,1,1);
 31	book(_h_m,4,1,3);
 32      }
 33      else if(inRange(sqrtS()/GeV,1.65,1.68)) {
 34	book(_h_x,4,1,2);
 35	book(_h_m,4,1,4);
 36      }
 37    }
 38
 39    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 40      for( const Particle &child : p.children()) {
 41	if(child.children().empty()) {
 42	  --nRes[child.pid()];
 43	  --ncount;
 44	}
 45	else
 46	  findChildren(child,nRes,ncount);
 47      }
 48    }
 49
 50    /// Perform the per-event analysis
 51    void analyze(const Event& event) {
 52      
 53      const FinalState& fs = apply<FinalState>(event, "FS");
 54
 55      map<long,int> nCount;
 56      int ntotal(0);
 57      Particle pip,pim;
 58      for (const Particle& p : fs.particles()) {
 59	nCount[p.pid()] += 1;
 60	++ntotal;
 61	if(p.pid()     == 211) pip=p;
 62	else if(p.pid()==-211) pim=p;
 63      }
 64      if(ntotal!=3) vetoEvent;
 65      if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==1)
 66	_c_total->fill();
 67      else
 68	vetoEvent;
 69      if(_h_x) {
 70	_h_x->fill(pip.momentum().p()/sqrtS());
 71	_h_x->fill(pim.momentum().p()/sqrtS());
 72	_h_m->fill((pip.momentum()+pim.momentum()).mass()/MeV);
 73      }
 74      const FinalState& ufs = apply<FinalState>(event, "UFS");
 75      for (const Particle& p : ufs.particles(Cuts::abspid==223 or
 76					     Cuts::abspid==113    or Cuts::abspid==213 or
 77					     Cuts::abspid==100113 or Cuts::abspid==100213)) {
 78	if(p.children().empty()) continue;
 79	map<long,int> nRes = nCount;
 80	int ncount = ntotal;
 81	findChildren(p,nRes,ncount);
 82	if(ncount!=1) continue;
 83	int idOther = 211;
 84	if(p.pid()==223 || p.pid()==113 || p.pid()==100113)
 85	  idOther = 111;
 86	else if(p.pid()==213 || p.pid()==100213)
 87	  idOther = -211;
 88	bool matched=true;
 89	for(auto const & val : nRes) {
 90	  if(val.first==idOther ) {
 91	    if(val.second !=1) {
 92	      matched = false;
 93	      break;
 94	    }
 95	  }
 96	  else if(val.second!=0) {
 97	    matched = false;
 98	    break;
 99	  }
100	}
101	if(!matched) continue;
102	if(matched) {
103	  if(p.pid()==223)
104	    _c_omega->fill();
105	  else if(p.pid()==213 || p.pid()==113)
106	    _c_rho->fill();
107	  else
108	    _c_rhop->fill();
109	  break;
110	}
111      }
112    }
113
114
115    /// Normalise histograms etc., after the run
116    void finalize() {
117      if(_h_x) {
118	normalize(_h_x,1.,false);
119	normalize(_h_m,1.,false);
120      }
121      double fact = crossSection()/nanobarn/sumOfWeights();
122      for(unsigned int ix=1;ix<4;++ix) {
123	unsigned int ymax = ix!=3 ? 2 : 4;
124	for(unsigned int iy=1;iy<ymax;++iy) {
125	  double sigma(0.),error(0.);
126	  if(ix<3) {
127	    sigma = _c_total->val()*fact;
128	    error = _c_total->err()*fact;
129	  }
130	  else if(ix==3) {
131	    if(iy==1) {
132	      sigma = _c_rho->val()*fact;
133	      error = _c_rho->err()*fact;
134	    }
135	    else if(iy==2) {
136	      sigma = _c_rhop->val()*fact;
137	      error = _c_rhop->err()*fact;
138	    }
139	    else {
140	      sigma = _c_omega->val()*fact;
141	      error = _c_omega->err()*fact;
142	    }
143	  }
144	  Scatter2D temphisto(refData(ix, 1, iy));
145	  Scatter2DPtr  mult;
146	  book(mult, ix, 1, iy);
147	  for (size_t b = 0; b < temphisto.numPoints(); b++) {
148	    const double x  = temphisto.point(b).x();
149	    pair<double,double> ex = temphisto.point(b).xErrs();
150	    pair<double,double> ex2 = ex;
151	    if(ex2.first ==0.) ex2. first=0.0001;
152	    if(ex2.second==0.) ex2.second=0.0001;
153	    if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
154	      mult->addPoint(x, sigma, ex, make_pair(error,error));
155	    }
156	    else {
157	      mult->addPoint(x, 0., ex, make_pair(0.,.0));
158	    }
159	  }
160	}
161      }
162    }
163
164    ///@}
165
166
167    /// @name Histograms
168    ///@{
169    CounterPtr _c_total,_c_omega,_c_rho,_c_rhop;
170    Histo1DPtr _h_x,_h_m;
171    ///@}
172
173
174  };
175
176
177  RIVET_DECLARE_PLUGIN(SND_2020_I1809286);
178
179}