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DM1_1978_I134061

Cross section for $e^+e^-\to \pi^+\pi^-$ between 0.483 and 1.096 GeV
Experiment: DM1 (ACO)
Inspire ID: 134061
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B76 (1978) 512-516, 1978
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to \pi^+\pi^-$ at energies between 0.483 and 1.096 GeV. Useful for comparing models of the pion form factor.

Source code: DM1_1978_I134061.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 DM1_1978_I134061 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(DM1_1978_I134061);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Initialise and register projections
22      declare(FinalState(), "FS");
23
24      // Book histograms
25      book(_npion, "TMP/pion");
26    }
27
28
29    /// Perform the per-event analysis
30    void analyze(const Event& event) {
31      const FinalState& fs = apply<FinalState>(event, "FS");
32      if(fs.particles().size()!=2) vetoEvent;
33      for (const Particle& p : fs.particles()) {
34	if(abs(p.pid())!=PID::PIPLUS) vetoEvent;
35      }
36      _npion->fill();
37    }
38
39
40    /// Normalise histograms etc., after the run
41    void finalize() {
42      double sigma = _npion->val();
43      double error = _npion->err();
44      sigma *= crossSection()/ sumOfWeights() /nanobarn;
45      error *= crossSection()/ sumOfWeights() /nanobarn; 
46      Scatter2D temphisto(refData(1, 1, 1));
47      Scatter2DPtr mult;
48      book(mult, 1, 1, 1);
49      for (size_t b = 0; b < temphisto.numPoints(); b++) {
50	const double x  = temphisto.point(b).x();
51	pair<double,double> ex = temphisto.point(b).xErrs();
52	pair<double,double> ex2 = ex;
53	if(ex2.first ==0.) ex2. first=0.0001;
54	if(ex2.second==0.) ex2.second=0.0001;
55	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
56	  mult->addPoint(x, sigma, ex, make_pair(error,error));
57	}
58	else {
59	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
60	}
61      }
62    }
63
64    //@}
65
66
67    /// @name Histograms
68    //@{
69    CounterPtr _npion;
70    //@}
71
72
73  };
74
75
76  // The hook for the plugin system
77  RIVET_DECLARE_PLUGIN(DM1_1978_I134061);
78
79
80}