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Rivet analyses reference

DM2_1988_I264144

Cross section for $e^+e^-\to\eta\pi^+\pi^-$ at energies between 1.35 and 2.4 GeV
Experiment: DM2 (DCI)
Inspire ID: 264144
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B212 (1988) 133-138, 1988
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Source code: DM2_1988_I264144.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 Add a short analysis description here
 10  class DM2_1988_I264144 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(DM2_1988_I264144);
 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(_numEtaPiPi, "TMP/EtaPiPi");
 27    }
 28
 29    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 30      for (const Particle &child : p.children()) {
 31	if(child.children().empty()) {
 32	  --nRes[child.pid()];
 33	  --ncount;
 34	}
 35	else
 36	  findChildren(child,nRes,ncount);
 37      }
 38    }
 39
 40    /// Perform the per-event analysis
 41    void analyze(const Event& event) {
 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      const FinalState& ufs = apply<FinalState>(event, "UFS");
 51      for (const Particle& p : ufs.particles()) {
 52	if(p.children().empty()) continue;
 53	// find the omega
 54	if(p.pid()==221) {
 55	  map<long,int> nRes = nCount;
 56	  int ncount = ntotal;
 57	  findChildren(p,nRes,ncount);
 58	  // eta pi+pi-
 59	  if(ncount!=2) continue;
 60	  bool matched = true;
 61	  for(auto const & val : nRes) {
 62	    if(abs(val.first)==211) {
 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	    _numEtaPiPi->fill();
 75	}
 76      }
 77    }
 78
 79
 80    /// Normalise histograms etc., after the run
 81    void finalize() {
 82      double sigma = _numEtaPiPi->val();
 83      double error = _numEtaPiPi->err();
 84      sigma *= crossSection()/ sumOfWeights() /nanobarn;
 85      error *= crossSection()/ sumOfWeights() /nanobarn; 
 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 _numEtaPiPi;
110    //@}
111
112
113  };
114
115
116  // The hook for the plugin system
117  RIVET_DECLARE_PLUGIN(DM2_1988_I264144);
118
119
120}