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SND_2014_I1321689

Cross section for $e^+e^-\to n\bar{n}$ between threshold and 2 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 1321689
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D90 (2014) 112007, 2014
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to n\bar{n}$ at energies between threshold and 2 GeV.

Source code: SND_2014_I1321689.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5
 6namespace Rivet {
 7
 8
 9  /// @brief e+ e- > n nbar
10  class SND_2014_I1321689 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2014_I1321689);
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      for(unsigned int ix=0;ix<2;++ix)
28        book(_nneutron[ix], 1+ix,1,1);
29
30    }
31
32
33    /// Perform the per-event analysis
34    void analyze(const Event& event) {
35      const FinalState& fs = apply<FinalState>(event, "FS");
36      if (fs.particles().size() != 2) vetoEvent;
37      for (const Particle& p : fs.particles()) {
38        if (p.abspid() != PID::NEUTRON) vetoEvent;
39      }
40      for(unsigned int ix=0;ix<2;++ix) _nneutron[ix]->fill(round(sqrtS()/MeV));
41    }
42
43
44    /// Normalise histograms etc., after the run
45    void finalize() {
46
47      for(unsigned int ix=0;ix<2;++ix)
48        scale(_nneutron[ix], crossSection()/ sumOfWeights() /nanobarn);
49    }
50
51    /// @}
52
53
54    /// @name Histograms
55    /// @{
56    BinnedHistoPtr<int> _nneutron[2];
57    /// @}
58
59
60  };
61
62
63  RIVET_DECLARE_PLUGIN(SND_2014_I1321689);
64
65
66}