rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

SND_2014_I1275333

Cross section for $e^+e^-\to\eta\gamma$ for energies between 1.07 and 2 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 1275333
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D90 (2014) 032002
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons below 0.6 and 1.38 GeV

Cross section for $e^+e^-\to\eta\gamma$ for energies between 1.07 and 2 GeV.

Source code: SND_2014_I1275333.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 Cross section for e+e- > gamma eta
 10  class SND_2014_I1275333 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2014_I1275333);
 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(_numEtaGamma, "TMP/EtaGamma");
 26    }
 27
 28    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 29      for (const Particle &child : p.children()) {
 30	if(child.children().empty()) {
 31	  --nRes[child.pid()];
 32	  --ncount;
 33	}
 34	else
 35	  findChildren(child,nRes,ncount);
 36      }
 37    }
 38
 39    /// Perform the per-event analysis
 40    void analyze(const Event& event) {
 41
 42      const FinalState& fs = apply<FinalState>(event, "FS");
 43
 44      map<long,int> nCount;
 45      int ntotal(0);
 46      for (const Particle& p : fs.particles()) {
 47	nCount[p.pid()] += 1;
 48	++ntotal;
 49      }
 50	 
 51      const FinalState& ufs = apply<FinalState>(event, "UFS");
 52      for (const Particle& p : ufs.particles(Cuts::pid==221)) {
 53	if(p.children().empty()) continue;
 54	// find the eta
 55	map<long,int> nRes = nCount;
 56	int ncount = ntotal;
 57	findChildren(p,nRes,ncount);
 58	// eta gamma
 59	if(ncount!=1) continue;
 60	bool matched = true;
 61	for(auto const & val : nRes) {
 62	  if(val.first==22) {
 63	    if(val.second !=1) {
 64	      matched = false;
 65	      break;
 66	    }
 67	  }
 68	  else if(val.second!=0) {
 69	    matched = false;
 70	    break;
 71	  }
 72	}
 73	if(matched)
 74	  _numEtaGamma->fill();
 75      }
 76    }
 77
 78
 79    /// Normalise histograms etc., after the run
 80    void finalize() {
 81
 82      double sigma = _numEtaGamma->val();
 83      double error = _numEtaGamma->err();
 84      sigma *= crossSection()/ sumOfWeights() /picobarn;
 85      error *= crossSection()/ sumOfWeights() /picobarn;
 86      Scatter2D temphisto(refData(1, 1, 1));
 87      Scatter2DPtr mult;
 88      book(mult, 1, 1, 1);
 89      for (size_t b = 0; b < temphisto.numPoints(); b++) {
 90	const double x  = temphisto.point(b).x();
 91	pair<double,double> ex = temphisto.point(b).xErrs();
 92	pair<double,double> ex2 = ex;
 93	if(ex2.first ==0.) ex2. first=0.0001;
 94	if(ex2.second==0.) ex2.second=0.0001;
 95	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
 96	  mult->addPoint(x, sigma, ex, make_pair(error,error));
 97	}
 98	else {
 99	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
100	}
101      }
102    }
103
104    //@}
105
106
107    /// @name Histograms
108    //@{
109    CounterPtr _numEtaGamma;
110    //@}
111
112
113  };
114
115
116  // The hook for the plugin system
117  RIVET_DECLARE_PLUGIN(SND_2014_I1275333);
118
119
120}