rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

SND_2020_I1800477

Cross section for $e^+e^-\to\eta\pi^0\gamma$ between 1.05 and 2 GeV
Experiment: SND (VEPP-2000)
Inspire ID: 1800477
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Cross section for $e^+e^-\to\eta\pi^0\gamma$ between 1.05 and 2 GeV by SND. The $\omega\eta$ and radiative subprocesses are also measured.

Source code: SND_2020_I1800477.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
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief e+e- > eta pi0 gamma
  class SND_2020_I1800477 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(SND_2020_I1800477);


    /// @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_omega, "/TMP/omega");
      book(_c_total, "/TMP/total");
    }

    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");
      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);
	// check eta pi0 gamma FS
	if(ncount!=2) continue;
	bool matched=true;
	for(auto const & val : nRes) {
	  if(abs(val.first)==22 || val.first==111 ) {
	    if(val.second !=1) {
	      matched = false;
	      break;
	    }
	  }
	  else if(val.second!=0) {
	    matched = false;
	    break;
	  }
	}
	if(!matched) continue;
	_c_total->fill();
	// check if from omega
	for (const Particle& p2 : ufs.particles()) {
	  if(p2.pid()!=223) 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)
	    _c_omega->fill();
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/picobarn/sumOfWeights();
      for(unsigned int ix=1;ix<4; ix+=2) {
       	double sigma(0.),error(0.);
       	if(ix==1) {
       	  sigma = _c_omega->val()*fact;
       	  error = _c_omega->err()*fact;
       	}
       	else if(ix==3) {
       	  sigma = _c_total->val()*fact;
       	  error = _c_total->err()*fact;
       	} 
       	Scatter2D temphisto(refData(ix, 1, 1));
       	Scatter2DPtr  mult;
       	book(mult, ix, 1, 1);
       	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_total,_c_omega;
    ///@}


  };


  DECLARE_RIVET_PLUGIN(SND_2020_I1800477);

}