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CMD2_2004_I630009

Cross section for $e^+e^-\to\pi^0\pi^0\gamma$ at energies between 0.6 and 0.97 GeV.
Experiment: CMD2 (VEPP-2M)
Inspire ID: 630009
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B580 (2004) 119-128, 2004
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Source code: CMD2_2004_I630009.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Add a short analysis description here
 9  class CMD2_2004_I630009 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2004_I630009);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21
22      // Initialise and register projections
23      declare(FinalState(), "FS");
24      book(_numPiPiGamma, "TMP/PiPiGamma");
25    }
26
27
28    /// Perform the per-event analysis
29    void analyze(const Event& event) {
30
31      const FinalState& fs = apply<FinalState>(event, "FS");
32
33      map<long,int> nCount;
34      int ntotal(0);
35      for (const Particle& p : fs.particles()) {
36	nCount[p.pid()] += 1;
37	++ntotal;
38      }
39      // three particles (pi0 pi0 gamma)
40      if(ntotal!=3) vetoEvent;
41      if(nCount[111]==2 && nCount[22]==1)
42	_numPiPiGamma->fill();
43    }
44
45
46    /// Normalise histograms etc., after the run
47    void finalize() {
48
49      double sigma = _numPiPiGamma->val();
50      double error = _numPiPiGamma->err();
51      sigma *= crossSection()/ sumOfWeights() /picobarn;
52      error *= crossSection()/ sumOfWeights() /picobarn;
53      Scatter2D temphisto(refData(1, 1, 1));
54      Scatter2DPtr mult;
55      book(mult, 1, 1, 1);
56      for (size_t b = 0; b < temphisto.numPoints(); b++) {
57	const double x  = temphisto.point(b).x();
58	pair<double,double> ex = temphisto.point(b).xErrs();
59	pair<double,double> ex2 = ex;
60	if(ex2.first ==0.) ex2. first=0.0001;
61	if(ex2.second==0.) ex2.second=0.0001;
62	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
63	  mult->addPoint(x, sigma, ex, make_pair(error,error));
64	}
65	else {
66	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
67	}
68      }
69
70    }
71
72    //@}
73
74
75    /// @name Histograms
76    //@{
77    CounterPtr _numPiPiGamma;
78    //@}
79
80
81  };
82
83
84  // The hook for the plugin system
85  RIVET_DECLARE_PLUGIN(CMD2_2004_I630009);
86
87
88}