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// -*- 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- > eta pi0 gamma
 10  class SND_2020_I1800477 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1800477);
 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      book(_c_omega, "/TMP/omega");
 27      book(_c_total, "/TMP/total");
 28    }
 29
 30    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 31      for( const Particle &child : p.children()) {
 32	if(child.children().empty()) {
 33	  --nRes[child.pid()];
 34	  --ncount;
 35	}
 36	else
 37	  findChildren(child,nRes,ncount);
 38      }
 39    }
 40
 41    /// Perform the per-event analysis
 42    void analyze(const Event& event) {
 43      
 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      const FinalState& ufs = apply<FinalState>(event, "UFS");
 53      for (const Particle& p : ufs.particles()) {
 54	if(p.children().empty()) continue;
 55	// find the eta
 56	if(p.pid()!=221) continue;
 57	map<long,int> nRes = nCount;
 58	int ncount = ntotal;
 59	findChildren(p,nRes,ncount);
 60	// check eta pi0 gamma FS
 61	if(ncount!=2) continue;
 62	bool matched=true;
 63	for(auto const & val : nRes) {
 64	  if(abs(val.first)==22 || val.first==111 ) {
 65	    if(val.second !=1) {
 66	      matched = false;
 67	      break;
 68	    }
 69	  }
 70	  else if(val.second!=0) {
 71	    matched = false;
 72	    break;
 73	  }
 74	}
 75	if(!matched) continue;
 76	_c_total->fill();
 77	// check if from omega
 78	for (const Particle& p2 : ufs.particles()) {
 79	  if(p2.pid()!=223) continue;
 80	  map<long,int> nResB = nRes;
 81	  int ncountB = ncount;
 82	  findChildren(p2,nResB,ncountB);
 83	  if(ncountB!=0) continue;
 84	  bool matched2 = true;
 85	  for(auto const & val : nResB) {
 86	    if(val.second!=0) {
 87	      matched2 = false;
 88	      break;
 89	    }
 90	  }
 91	  if(matched2)
 92	    _c_omega->fill();
 93	}
 94      }
 95    }
 96
 97
 98    /// Normalise histograms etc., after the run
 99    void finalize() {
100      double fact = crossSection()/picobarn/sumOfWeights();
101      for(unsigned int ix=1;ix<4; ix+=2) {
102       	double sigma(0.),error(0.);
103       	if(ix==1) {
104       	  sigma = _c_omega->val()*fact;
105       	  error = _c_omega->err()*fact;
106       	}
107       	else if(ix==3) {
108       	  sigma = _c_total->val()*fact;
109       	  error = _c_total->err()*fact;
110       	} 
111       	Scatter2D temphisto(refData(ix, 1, 1));
112       	Scatter2DPtr  mult;
113       	book(mult, ix, 1, 1);
114       	for (size_t b = 0; b < temphisto.numPoints(); b++) {
115      	  const double x  = temphisto.point(b).x();
116      	  pair<double,double> ex = temphisto.point(b).xErrs();
117      	  pair<double,double> ex2 = ex;
118      	  if(ex2.first ==0.) ex2. first=0.0001;
119      	  if(ex2.second==0.) ex2.second=0.0001;
120      	  if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
121      	    mult->addPoint(x, sigma, ex, make_pair(error,error));
122      	  }
123      	  else {
124      	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
125      	  }
126       	}
127      }
128    }
129
130    ///@}
131
132
133    /// @name Histograms
134    ///@{
135    CounterPtr _c_total,_c_omega;
136    ///@}
137
138
139  };
140
141
142  RIVET_DECLARE_PLUGIN(SND_2020_I1800477);
143
144}