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SND_2000_I527752

Cross section for $e^+e^-\to\omega\pi^0\to\pi^0\pi^0\gamma$ for energies below 1.4 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 527752
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B486 (2000) 29-34, 2000
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Source code: SND_2000_I527752.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 SND_2000_I527752 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2000_I527752);
 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(_numOmegaPi, "TMP/OmegaPi");
 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()]+=1;
 33	  ++ncount;
 34	}
 35	else
 36	  findChildren(child,nRes,ncount);
 37      }
 38    }
 39
 40
 41    /// Perform the per-event analysis
 42    void analyze(const Event& event) {
 43      const FinalState& fs = apply<FinalState>(event, "FS");
 44
 45      map<long,int> nCount;
 46      int ntotal(0);
 47      for (const Particle& p : fs.particles()) {
 48	nCount[p.pid()] += 1;
 49	++ntotal;
 50      }
 51      // three particles (pi0 pi0 gamma)
 52      if(ntotal!=3) vetoEvent;
 53      const FinalState& ufs = apply<FinalState>(event, "UFS");
 54      for (const Particle& p : ufs.particles()) {
 55	if(p.children().empty()) continue;
 56	// find the omega
 57	if(p.pid()==223) {
 58	  map<long,int> nRes;
 59	  int ncount(0);
 60	  findChildren(p,nRes,ncount);
 61	  // only omega to pi0 gamma mode
 62	  if(ncount!=2) continue;
 63	  if(nRes[111]!=1 || nRes[22]!=1) continue;
 64	  // omega pi0
 65	  if(nCount[111]-nRes[111]==1)
 66	    _numOmegaPi->fill();
 67	}
 68      }
 69    }
 70
 71
 72    /// Normalise histograms etc., after the run
 73    void finalize() {
 74
 75      double sigma = _numOmegaPi->val();
 76      double error = _numOmegaPi->err();
 77      sigma *= crossSection()/ sumOfWeights() /nanobarn;
 78      error *= crossSection()/ sumOfWeights() /nanobarn;
 79      Scatter2D temphisto(refData(1, 1, 1));
 80      Scatter2DPtr mult;
 81      book(mult, 1, 1, 1);
 82      for (size_t b = 0; b < temphisto.numPoints(); b++) {
 83	const double x  = temphisto.point(b).x();
 84	pair<double,double> ex = temphisto.point(b).xErrs();
 85	pair<double,double> ex2 = ex;
 86	if(ex2.first ==0.) ex2. first=0.0001;
 87	if(ex2.second==0.) ex2.second=0.0001;
 88	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
 89	  mult->addPoint(x, sigma, ex, make_pair(error,error));
 90	}
 91	else {
 92	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
 93	}
 94      } 
 95    }
 96
 97    //@}
 98
 99    /// @name Histograms
100    //@{
101    CounterPtr _numOmegaPi;
102    //@}
103
104
105  };
106
107
108  // The hook for the plugin system
109  RIVET_DECLARE_PLUGIN(SND_2000_I527752);
110
111
112}