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SND_2020_I1789269

Cross section for $e^+e^-\to \pi^+\pi^-$ at energies between 0.525 and 0.883 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 1789269
Status: VALIDATED
Authors:
  • Peter Richardson
References: 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 0.525 and 0.883 GeV

Source code: SND_2020_I1789269.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+e- -> pi+pi-
 9  class SND_2020_I1789269 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1789269);
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
25      // Book histograms
26      book(_npion, "TMP/pion");
27    }
28
29
30    /// Perform the per-event analysis
31    void analyze(const Event& event) {
32      const FinalState& fs = apply<FinalState>(event, "FS");
33      if(fs.particles().size()!=2) vetoEvent;
34      for (const Particle& p : fs.particles()) {
35	if(abs(p.pid())!=PID::PIPLUS) vetoEvent;
36      }
37      _npion->fill();
38    }
39
40
41    /// Normalise histograms etc., after the run
42    void finalize() {
43      double sigma = _npion->val();
44      double error = _npion->err();
45      sigma *= crossSection()/ sumOfWeights() /nanobarn;
46      error *= crossSection()/ sumOfWeights() /nanobarn;
47      Estimate1DPtr mult;
48      book(mult, 1, 1, 4);
49      for (auto& b : mult->bins()) {
50        if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
51          b.set(sigma, error);
52        }
53      }
54    }
55
56    /// @}
57
58
59    /// @name Histograms
60    /// @{
61    CounterPtr _npion;
62    /// @}
63
64
65  };
66
67
68  RIVET_DECLARE_PLUGIN(SND_2020_I1789269);
69
70}