1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+ e- > KS0 KL0
 9  class BESIII_2024_I2738509 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2738509);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      declare(FinalState(), "FS");
22      book(_nK0K0, 1, 1, 2);
23      for (const string& en : _nK0K0.binning().edges<0>()) {
24        const double end = std::stod(en)*GeV;
25        if (isCompatibleWithSqrtS(end)) {
26          _ecms = en;
27          break;
28        }
29      }
30      if (_ecms.empty())
31        MSG_ERROR("Beam energy incompatible with analysis.");
32    }
33
34
35    /// Perform the per-event analysis
36    void analyze(const Event& event) {
37      const FinalState& fs = apply<FinalState>(event, "FS");
38
39      map<long,int> nCount;
40      int ntotal(0);
41      for (const Particle& p : fs.particles()) {
42        nCount[p.pid()] += 1;
43        ++ntotal;
44      }
45
46      if(ntotal==2 && nCount[130]==1 && nCount[310]==1)
47        _nK0K0->fill(_ecms);
48    }
49
50
51    /// Normalise histograms etc., after the run
52    void finalize() {
53      scale(_nK0K0, crossSection()/ sumOfWeights() /picobarn);
54    }
55
56    /// @}
57
58
59    /// @name Histograms
60    /// @{
61    BinnedHistoPtr<string> _nK0K0;
62    string _ecms;
63    /// @}
64
65
66  };
67
68
69  RIVET_DECLARE_PLUGIN(BESIII_2024_I2738509);
70
71}