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Rivet analyses reference

DM2_1989_I267118

Cross section for $e^+e^-\to \pi^+\pi^-$ between 1.35 and 2.4 GeV
Experiment: DM2 (DCI)
Inspire ID: 267118
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B220 (1989) 321-327, 1989
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 1.35 and 2.4 GeV. Useful for comparing models of the pion form factor.

Source code: DM2_1989_I267118.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 DM2_1989_I267118 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(DM2_1989_I267118);
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
26      // Book histograms
27      book(_npion, "TMP/pion");
28    }
29
30
31    /// Perform the per-event analysis
32    void analyze(const Event& event) {
33      const FinalState& fs = apply<FinalState>(event, "FS");
34      if(fs.particles().size()!=2) vetoEvent;
35      for (const Particle& p : fs.particles()) {
36	if(abs(p.pid())!=PID::PIPLUS) vetoEvent;
37      }
38      _npion->fill();
39    }
40
41
42    /// Normalise histograms etc., after the run
43    void finalize() {
44      double sigma = _npion->val();
45      double error = _npion->err();
46      sigma *= crossSection()/ sumOfWeights() /nanobarn;
47      error *= crossSection()/ sumOfWeights() /nanobarn;
48      Estimate1DPtr mult;
49      book(mult, 1, 1, 1);
50      for (auto& b : mult->bins()) {
51        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
52          b.set(sigma, error);
53        }
54      }
55    }
56
57    /// @}
58
59
60    /// @name Histograms
61    /// @{
62    CounterPtr _npion;
63    /// @}
64
65
66  };
67
68
69  RIVET_DECLARE_PLUGIN(DM2_1989_I267118);
70
71
72}