1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief e+e- to pi+pi- J/psi
 9  class BESIII_2013_I1225275 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1225275);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // projections
22      declare(FinalState(), "FS");
23      // histograms
24      book(_h_sigma, 1,1,1);
25      for (unsigned int ix=0;ix<3;++ix) {
26        book(_h_mass[ix], 2, 1, 1+ix);
27      }
28      book(_h_mass[3], 3, 1, 1);
29    }
30
31
32    /// Perform the per-event analysis
33    void analyze(const Event& event) {
34      Particles fs = apply<FinalState>(event, "FS").particles();
35      Particles PSI, other;
36      for (const Particle& p : fs) {
37        Particle parent=p;
38       	while (!parent.parents().empty()) {
39      	  parent=parent.parents()[0];
40          if (parent.abspid()==PID::JPSI) break;
41        }
42        if (parent.abspid()!=PID::JPSI) {
43          other.push_back(p);
44          continue;
45        }
46        bool found=false;
47        for (auto & p : PSI) {
48      	  // psi already in list
49      	  if (fuzzyEquals(p.mom(), parent.mom())) {
50      	    found=true;
51      	    break;
52      	  }
53      	}
54      	if (!found) PSI.push_back(parent);
55      }
56      // J/psi + 2 other particles
57      if (PSI.size()!=1 || other.size()!=2) vetoEvent;
58      // other particles pi+ pi-
59      if (!(other[0].pid()==-other[1].pid() && other[0].abspid()==PID::PIPLUS)) vetoEvent;
60      if (other[0].pid()<0) swap(other[0],other[1]);
61      // cross secrtion
62      _h_sigma->fill("4.26"s);
63      // fill the mass plots
64      double mJpsipi[2] = {(other[0].mom()+PSI[0].mom()).mass(),
65                           (other[1].mom()+PSI[0].mom()).mass()};
66      for (unsigned int ix=0; ix<2; ++ix) {
67        _h_mass[ix]->fill(mJpsipi[ix]);
68      }
69      _h_mass[2]->fill((other[0].mom()+other[1].mom()).mass());
70      _h_mass[3]->fill(max(mJpsipi[0],mJpsipi[1]));
71    }
72
73
74    /// Normalise histograms etc., after the run
75    void finalize() {
76      scale(_h_sigma, crossSection()/ sumOfWeights() /picobarn);
77      normalize(_h_mass, 1.0, false);
78    }
79
80    /// @}
81
82
83    /// @name Histograms
84    /// @{
85    BinnedHistoPtr<string> _h_sigma;
86    Histo1DPtr _h_mass[4];
87    /// @}
88
89
90  };
91
92
93  RIVET_DECLARE_PLUGIN(BESIII_2013_I1225275);
94
95}