1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief psi(2S) -> J/psi pi+pi-
 9  class MARKII_1979_I144382 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1979_I144382);
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(UnstableParticles(),"UFS");
24      book(_hist, 1, 1, 1);
25
26    }
27
28
29    void findDecayProducts(const Particle & mother,
30			   unsigned int & nstable,
31			   Particles& pip, Particles& pim,
32			   Particles & onium) {
33      for(const Particle & p : mother.children()) {
34        int id = p.pid();
35      	if ( id == PID::PIMINUS) {
36	  pim.push_back(p);
37	  ++nstable;
38	}
39       	else if (id == PID::PIPLUS) {
40       	  pip.push_back(p);
41       	  ++nstable;
42       	}
43	else if (id==443) {
44	  onium.push_back(p);
45	  ++nstable;
46	}
47	else if ( !p.children().empty() ) {
48	  findDecayProducts(p,nstable,pip,pim,onium);
49	}
50	else
51	  ++nstable;
52      }
53    }
54
55    /// Perform the per-event analysis
56    void analyze(const Event& event) {
57      // loop over unstable particles
58      for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==100443)) {
59      	unsigned int nstable(0);
60      	Particles pip, pim, onium;
61      	findDecayProducts(ups,nstable,pip,pim,onium);
62      	// check for onium
63      	if(onium.size() !=1 || nstable !=3 || pip.size()!=1 || pim.size() !=1 ) continue;
64      	FourMomentum q = pip[0].momentum()+pim[0].momentum();
65      	_hist->fill(q.mass2());
66      }
67    }
68
69
70    /// Normalise histograms etc., after the run
71    void finalize() {
72      normalize(_hist);
73    }
74
75    ///@}
76
77
78    /// @name Histograms
79    ///@{
80    Histo1DPtr _hist;
81    ///@}
82
83
84  };
85
86
87  RIVET_DECLARE_PLUGIN(MARKII_1979_I144382);
88
89}