1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Cross-section for $K^0_SK^\pm\pi^\mp$ between 3.8 and 4.6 GeV
 9  class BESIII_2018_I1691798 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1691798);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Initialise and register projections
22      declare(FinalState(), "FS");
23      book(_nKKpi, "/TMP/nKKpi" );
24    }
25
26
27    /// Perform the per-event analysis
28    void analyze(const Event& event) {
29      const FinalState& fs = apply<FinalState>(event, "FS");
30
31      map<long,int> nCount;
32      int ntotal(0);
33      for (const Particle& p : fs.particles()) {
34        nCount[p.pid()] += 1;
35        ++ntotal;
36      }
37
38      if(ntotal==3 && nCount[310]==1 &&
39         ((nCount[ 321]=1 &&  nCount[-211] ==1) ||
40          (nCount[-321]=1 &&  nCount[ 211] ==1)))
41        _nKKpi->fill();
42    }
43
44
45    /// Normalise histograms etc., after the run
46    void finalize() {
47      double sigma = _nKKpi->val();
48      double error = _nKKpi->err();
49      sigma *= crossSection()/ sumOfWeights() /picobarn;
50      error *= crossSection()/ sumOfWeights() /picobarn;
51      Estimate1DPtr  mult;
52      book(mult, 1, 1, 1);
53      for (auto& b : mult->bins()) {
54        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
55          b.set(sigma, error);
56        }
57      }
58    }
59
60    /// @}
61
62
63    /// @name Histograms
64    /// @{
65    CounterPtr _nKKpi;
66    /// @}
67
68
69  };
70
71
72  RIVET_DECLARE_PLUGIN(BESIII_2018_I1691798);
73
74
75}