1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Cross section for $e^+e^-\to K^+K^-$ between 2.00 and 3.08 GeV
 9  class BESIII_2018_I1704558 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1704558);
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(_nkaon, "TMP/kaon");
27
28    }
29
30
31    /// Perform the per-event analysis
32    void analyze(const Event& event) {
33      const FinalState& fs = apply<FinalState>(event, "FS");
34      if(fs.particles().size()!=2) vetoEvent;
35      for (const Particle& p : fs.particles()) {
36        if(abs(p.pid())!=PID::KPLUS) vetoEvent;
37      }
38      _nkaon->fill();
39    }
40
41
42    /// Normalise histograms etc., after the run
43    void finalize() {
44      double sigma = _nkaon->val();
45      double error = _nkaon->err();
46      sigma *= crossSection()/ sumOfWeights() /picobarn;
47      error *= crossSection()/ sumOfWeights() /picobarn;
48      Estimate1DPtr  mult;
49      book(mult, 1, 1, 1);
50      for (auto& b : mult->bins()) {
51        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
52          b.set(sigma, error);
53        }
54      }
55    }
56
57    /// @}
58
59
60    /// @name Histograms
61    /// @{
62    CounterPtr _nkaon;
63    /// @}
64
65
66  };
67
68
69  RIVET_DECLARE_PLUGIN(BESIII_2018_I1704558);
70
71
72}