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SND_2003_I612867

Cross section for $e^+e^-\to\pi\gamma$ for energies between 600 MeV and 970 MeV
Experiment: SND (VEPP-2M)
Inspire ID: 612867
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys. Lett. B559, 171 (2003)
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons below 0.6 and 1.38 GeV

Cross section for $e^+e^-\to\pi\gamma$ for energies between 600 MeV and 970 MeV

Source code: SND_2003_I612867.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5
 6namespace Rivet {
 7
 8
 9  /// @brief Add a short analysis description here
10  class SND_2003_I612867 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2003_I612867);
15
16
17    /// @name Analysis methods
18    //@{
19
20    /// Book histograms and initialise projections before the run
21    void init() {
22      declare(FinalState(), "FS");
23      book(_numPi0Gamma, "TMP/Pi0Gamma");
24    }
25
26
27    /// Perform the per-event analysis
28    void analyze(const Event& event) {
29
30      const FinalState& fs = apply<FinalState>(event, "FS");
31
32      map<long,int> nCount;
33      int ntotal(0);
34      for (const Particle& p : fs.particles()) {
35	nCount[p.pid()] += 1;
36	++ntotal;
37      }
38      if(ntotal==2 && nCount[22]==1 && nCount[111]==1)
39	_numPi0Gamma->fill();
40
41    }
42
43
44    /// Normalise histograms etc., after the run
45    void finalize() {
46
47      double sigma = _numPi0Gamma->val();
48      double error = _numPi0Gamma->err();
49      sigma *= crossSection()/ sumOfWeights() /nanobarn;
50      error *= crossSection()/ sumOfWeights() /nanobarn;
51      Scatter2D temphisto(refData(1, 1, 1));
52      Scatter2DPtr mult;
53      book(mult, 1, 1, 1);
54      for (size_t b = 0; b < temphisto.numPoints(); b++) {
55	const double x  = temphisto.point(b).x();
56	pair<double,double> ex = temphisto.point(b).xErrs();
57	pair<double,double> ex2 = ex;
58	if(ex2.first ==0.) ex2. first=0.0001;
59	if(ex2.second==0.) ex2.second=0.0001;
60	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
61	  mult->addPoint(x, sigma, ex, make_pair(error,error));
62	}
63	else {
64	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
65	}
66      }
67    }
68
69    //@}
70
71
72    /// @name Histograms
73    //@{
74    CounterPtr _numPi0Gamma;
75    //@}
76
77
78  };
79
80
81  // The hook for the plugin system
82  RIVET_DECLARE_PLUGIN(SND_2003_I612867);
83
84
85}