rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

SND_2019_I1726419

Cross section for $e^+e^-\to\pi^+\pi^-\pi^0\eta$ for energies below 2 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 1726419
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 $\omega\eta$, $\phi\eta$ and $a_0(980)\rho$, for energies below 2 GeV by the SND experiment

Source code: SND_2019_I1726419.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief SND pi+pi-pi0eta cross section
  class SND_2019_I1726419 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(SND_2019_I1726419);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");


      book(_c_all  , "/TMP/all");
      book(_c_omega, "/TMP/omega");
      book(_c_phi  , "/TMP/phi");
      book(_c_rho  , "/TMP/rho");
    }


    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for( const Particle &child : p.children()) {
	if(child.children().empty()) {
	  --nRes[child.pid()];
	  --ncount;
	}
	else
	  findChildren(child,nRes,ncount);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      
      const FinalState& fs = apply<FinalState>(event, "FS");

      map<long,int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
	nCount[p.pid()] += 1;
	++ntotal;
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      bool found = false, foundOmegaPhi = false;
      for (const Particle& p : ufs.particles()) {
	if(p.children().empty()) continue;
	// find the eta
	if(p.pid()!=221) continue;
	map<long,int> nRes = nCount;
	int ncount = ntotal;
	findChildren(p,nRes,ncount);
	// eta pi+pi-
	if(ncount==3) {
	  bool matched = true;
	  for(auto const & val : nRes) {
	    if(abs(val.first)==211 || val.first==111 ) {
	      if(val.second !=1) {
		matched = false;
		break;
	      }
	    }
	    else if(val.second!=0) {
	      matched = false;
	      break;
	    }
	  }
	  if(matched) {
	    _c_all->fill();
	    found = true;
	  }
	}
	for (const Particle& p2 : ufs.particles()) {
	  if(p2.pid()!=223 && p2.pid()!=333) continue;
	  map<long,int> nResB = nRes;
	  int ncountB = ncount;
	  findChildren(p2,nResB,ncountB);
	  if(ncountB!=0) continue;
	  bool matched2 = true;
	  for(auto const & val : nResB) {
	    if(val.second!=0) {
	      matched2 = false;
	      break;
	    }
	  }
	  if(matched2) {
	    if(p2.pid()==223)
	      _c_omega->fill();
	    else if(p2.pid()==333)
	      _c_phi->fill();
	    foundOmegaPhi=true;
	  }
	}
      }
      if(found && !foundOmegaPhi)
	_c_rho->fill();
    }
    

    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/nanobarn/sumOfWeights();
      for(unsigned int ix=1;ix<5;++ix) {
	double sigma(0.),error(0.);
	if(ix==1) {
	  sigma = _c_all->val()*fact;
	  error = _c_all->err()*fact;
	}
	else if(ix==2) {
	  sigma = _c_omega->val()*fact;
	  error = _c_omega->err()*fact;
	}
	else if(ix==3) {
	  sigma = _c_phi->val()*fact;
	  error = _c_phi->err()*fact;
	}
	else if(ix==4) {
	  sigma = _c_rho->val()*fact;
	  error = _c_rho->err()*fact;
	} 
	Scatter2D temphisto(refData(1, 1, ix));
	Scatter2DPtr  mult;
	book(mult, 1, 1, ix);
	for (size_t b = 0; b < temphisto.numPoints(); b++) {
	  const double x  = temphisto.point(b).x();
	  pair<double,double> ex = temphisto.point(b).xErrs();
	  pair<double,double> ex2 = ex;
	  if(ex2.first ==0.) ex2. first=0.0001;
	  if(ex2.second==0.) ex2.second=0.0001;
	  if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
	    mult->addPoint(x, sigma, ex, make_pair(error,error));
	  }
	  else {
	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
	  }
	}
      }
    }

    //@}


    /// @name Histograms
    //@{
    CounterPtr _c_all, _c_omega, _c_phi,_c_rho;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(SND_2019_I1726419);


}