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BESIII_2019_I1736235

Cross section for $e^+e^-\to$ proton and antiproton between 2. and 3.08 GeV
Experiment: BESIII (BEPC II)
Inspire ID: 1736235
Status: VALIDATED
Authors:
  • Peter Richardson
References: 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); (1.2, 1.2); (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.4, 1.4); (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 using. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: BESIII_2019_I1736235.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+e- > p pbar
 9  class BESIII_2019_I1736235 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1736235);
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, 1);
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()) MSG_ERROR("Beam energy incompatible with analysis.");
35    }
36
37
38    /// Perform the per-event analysis
39    void analyze(const Event& event) {
40      const FinalState& fs = apply<FinalState>(event, "FS");
41      if(fs.particles().size()!=2) vetoEvent;
42      for (const Particle& p :  fs.particles()) {
43        if(abs(p.pid())!=PID::PROTON) vetoEvent;
44      }
45      _nproton->fill(_ecms);
46    }
47
48
49    /// Normalise histograms etc., after the run
50    void finalize() {
51      scale(_nproton, crossSection()/ sumOfWeights() /picobarn);
52    }
53
54    /// @}
55
56
57    /// @name Histograms
58    /// @{
59    BinnedHistoPtr<string> _nproton;
60    string _ecms;
61    /// @}
62
63
64  };
65
66
67  RIVET_DECLARE_PLUGIN(BESIII_2019_I1736235);
68
69}