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BESIII_2014_I1286898

Cross section for $e^+e^-\to$ proton and antiproton between 3.65 and 3.9 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1286898
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B735 (2014) 101-107, 2014
Beams: e+ e-
Beam energies: (1.8, 1.8); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9) GeV
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to p\bar{p}$ for energies between 3.65 and 3.9 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: BESIII_2014_I1286898.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Cross section for $e^+e^-\to$ proton and antiproton between 3.65 and 3.9 GeV
 9  class BESIII_2014_I1286898 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2014_I1286898);
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(_nproton, 1, 1, 6);
27      for (const string& en : _nproton.binning().edges<0>()) {
28        const double end = std::stod(en)*GeV;
29        if (isCompatibleWithSqrtS(end)) {
30          _ecms = en;
31          break;
32        }
33      }
34      if (_ecms.empty())
35        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::PROTON) vetoEvent;
45      }
46      _nproton->fill(_ecms);
47    }
48
49
50    /// Normalise histograms etc., after the run
51    void finalize() {
52      scale(_nproton, crossSection()/ sumOfWeights() /picobarn);
53    }
54
55    /// @}
56
57
58    /// @name Histograms
59    /// @{
60    BinnedHistoPtr<string> _nproton;
61    string _ecms;
62    /// @}
63
64
65  };
66
67
68  RIVET_DECLARE_PLUGIN(BESIII_2014_I1286898);
69
70}