1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+e- to 3 pi from BES
 9  class BESIII_2019_I1773081 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1773081);
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(_num3pi, "TMP/num3");
26
27    }
28
29
30    /// Perform the per-event analysis
31    void analyze(const Event& event) {
32      const FinalState& fs = apply<FinalState>(event, "FS");
33
34      map<long,int> nCount;
35      int ntotal(0);
36      for (const Particle& p : fs.particles()) {
37        nCount[p.pid()] += 1;
38        ++ntotal;
39      }
40      if(ntotal!=3) vetoEvent;
41      if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==1)
42        _num3pi->fill();
43
44    }
45
46
47    /// Normalise histograms etc., after the run
48    void finalize() {
49
50      double sigma = _num3pi->val();
51      double error = _num3pi->err();
52      sigma *= crossSection()/ sumOfWeights() /nanobarn;
53      error *= crossSection()/ sumOfWeights() /nanobarn;
54      Estimate1DPtr  mult;
55      book(mult, 1, 1, 1);
56      for (auto& b : mult->bins()) {
57        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
58          b.set(sigma, error);
59        }
60      }
61    }
62
63    /// @}
64
65
66    /// @name Histograms
67    /// @{
68    CounterPtr _num3pi;
69    /// @}
70
71  };
72
73
74  RIVET_DECLARE_PLUGIN(BESIII_2019_I1773081);
75
76}