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DM1_1981_I166964

Cross section for $e^+e^-\to\omega\pi^+\pi^-$ at energies between 1.4 and 2.2 GeV
Experiment: DM1 (DCI)
Inspire ID: 166964
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B106 (1981) 155-158, 1981
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\omega\pi^+\pi^-$ at energies between 1.4 and 2.2 GeV.

Source code: DM1_1981_I166964.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 DM1_1981_I166964 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(DM1_1981_I166964);
 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(_nomega, "TMP/omega");
 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      const FinalState& fs = apply<FinalState>(event, "FS");
 42      
 43      map<long,int> nCount;
 44      int ntotal(0);
 45      for (const Particle& p : fs.particles()) {
 46	nCount[p.pid()] += 1;
 47	++ntotal;
 48      }
 49      const FinalState& ufs = apply<FinalState>(event, "UFS");
 50      for (const Particle& p : ufs.particles()) {
 51	if(p.children().empty()) continue;
 52	// find the omega
 53	if(p.pid()==223) {
 54	  map<long,int> nRes = nCount;
 55	  int ncount = ntotal;
 56	  findChildren(p,nRes,ncount);
 57	  // omega pi+pi-
 58	  if(ncount!=2) continue;
 59	  bool matched = true;
 60	  for(auto const & val : nRes) {
 61	    if(abs(val.first)==211) {
 62	      if(val.second !=1) {
 63		matched = false;
 64		break;
 65	      }
 66	    }
 67	    else if(val.second!=0) {
 68	      matched = false;
 69	      break;
 70	    }
 71	  }
 72	  if(matched)
 73	    _nomega->fill();
 74	}
 75      }
 76    }
 77
 78
 79    /// Normalise histograms etc., after the run
 80    void finalize() {
 81      double fact = crossSection()/ sumOfWeights() /nanobarn;
 82      double sigma = _nomega->val()*fact;
 83      double error = _nomega->err()*fact; 
 84      Scatter2D temphisto(refData(1, 1, 1));
 85      Scatter2DPtr mult;
 86      book(mult, 1, 1, 1);
 87      for (size_t b = 0; b < temphisto.numPoints(); b++) {
 88	const double x  = temphisto.point(b).x();
 89	pair<double,double> ex = temphisto.point(b).xErrs();
 90	pair<double,double> ex2 = ex;
 91	if(ex2.first ==0.) ex2. first=0.0001;
 92	if(ex2.second==0.) ex2.second=0.0001;
 93	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
 94	  mult->addPoint(x, sigma, ex, make_pair(error,error));
 95	}
 96	else {
 97	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
 98	}
 99      }
100    }
101
102    //@}
103
104
105    /// @name Histograms
106    //@{
107    CounterPtr _nomega;
108    //@}
109
110
111  };
112
113
114  // The hook for the plugin system
115  RIVET_DECLARE_PLUGIN(DM1_1981_I166964);
116
117
118}