rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BESIII_2021_I1966612

Cross section for $e^+e^-\to$ neutron and antineutron between 2. and 3.08 GeV
Experiment: BESIII (BEPC II)
Inspire ID: 1966612
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Nature Phys. 17 (2021) 11, 1200-1204
Beams: e+ e-
Beam energies: (1.0, 1.0); (1.0, 1.0); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.2, 1.2); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3); (1.4, 1.4); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5) GeV
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to p\bar{p}$ for energies between 2. and 3.08 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: BESIII_2021_I1966612.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+ e- > n nbar
 9  class BESIII_2021_I1966612 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1966612);
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(_nneutron, 1, 1, 1);
27
28      for (const string& en : _nneutron.binning().edges<0>()) {
29        const double end = std::stod(en)*GeV;
30        if (isCompatibleWithSqrtS(end)) {
31          _ecms = en;
32          break;
33        }
34      }
35      if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
36    }
37
38
39    /// Perform the per-event analysis
40    void analyze(const Event& event) {
41      const FinalState& fs = apply<FinalState>(event, "FS");
42      if(fs.particles().size()!=2) vetoEvent;
43      for (const Particle& p :  fs.particles()) {
44	if(abs(p.pid())!=PID::NEUTRON) vetoEvent;
45      }
46      _nneutron->fill(_ecms);
47    }
48
49
50    /// Normalise histograms etc., after the run
51    void finalize() {
52      scale(_nneutron, crossSection()/ sumOfWeights() /picobarn);
53    }
54
55    ///@}
56
57
58    /// @name Histograms
59    ///@{
60    BinnedHistoPtr<string> _nneutron;
61    string _ecms;
62    ///@}
63
64
65  };
66
67
68  RIVET_DECLARE_PLUGIN(BESIII_2021_I1966612);
69
70}