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" , refData(1,1,1));
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(sqrtS()/GeV);
43
44    }
45
46
47    /// Normalise histograms etc., after the run
48    void finalize() {
49      scale(_num3pi, crossSection()/ sumOfWeights() /nanobarn);
50      Estimate1DPtr  mult;
51      book(mult, 1, 1, 1);
52      barchart(_num3pi,mult);
53    }
54
55    /// @}
56
57
58    /// @name Histograms
59    /// @{
60    Histo1DPtr _num3pi;
61    /// @}
62
63  };
64
65
66  RIVET_DECLARE_PLUGIN(BESIII_2019_I1773081);
67
68}