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      Scatter2D temphisto(refData(1, 1, 1));
55      Scatter2DPtr  mult;
56      book(mult, 1, 1, 1);
57      for (size_t b = 0; b < temphisto.numPoints(); b++) {
58	const double x  = temphisto.point(b).x();
59	pair<double,double> ex = temphisto.point(b).xErrs();
60	pair<double,double> ex2 = ex;
61	if(ex2.first ==0.) ex2. first=0.0001;
62	if(ex2.second==0.) ex2.second=0.0001;
63	if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
64	  mult->addPoint(x, sigma, ex, make_pair(error,error));
65	}
66	else {
67	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
68	}
69      }
70    }
71
72    //@}
73
74
75    /// @name Histograms
76    //@{
77    CounterPtr _num3pi;
78    //@}
79
80
81  };
82
83
84  RIVET_DECLARE_PLUGIN(BESIII_2019_I1773081);
85
86}