1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Upsilon(4S) -> Upsilon(1S) pi+pi-
 9  class BELLE_2009_I810744 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2009_I810744);
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    void findDecayProducts(const Particle & mother,
29			   unsigned int & nstable,
30			   Particles& pip, Particles& pim,
31			   Particles & onium) {
32      for(const Particle & p : mother.children()) {
33        int id = p.pid();
34      	if ( id == PID::PIMINUS) {
35	  pim.push_back(p);
36	  ++nstable;
37	}
38       	else if (id == PID::PIPLUS) {
39       	  pip.push_back(p);
40       	  ++nstable;
41       	}
42       	else if (id == PID::PI0) {
43       	  ++nstable;
44       	}
45	else if (id==553) {
46	  onium.push_back(p);
47	  ++nstable;
48	}
49	else if ( !p.children().empty() ) {
50	  findDecayProducts(p,nstable,pip,pim,onium);
51	}
52	else
53	  ++nstable;
54      }
55    }
56
57    /// Perform the per-event analysis
58    void analyze(const Event& event) {
59      // loop over unstable particles
60      for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==300553)) {
61	unsigned int nstable(0);
62	Particles pip, pim, onium;
63	findDecayProducts(ups,nstable,pip,pim,onium);
64	// check for onium
65	if(onium.size() !=1 || nstable !=3) continue;
66	// check for pipi
67	if( ! (pip.size()==1 && pim.size() ==1) ) continue;
68	FourMomentum q = pip[0].momentum()+pim[0].momentum();
69	_hist->fill(q.mass());
70      }
71    }
72
73
74    /// Normalise histograms etc., after the run
75    void finalize() {
76      normalize(_hist);
77    }
78
79    /// @}
80
81
82    /// @name Histograms
83    /// @{
84    Histo1DPtr _hist;
85    /// @}
86
87
88  };
89
90
91  RIVET_DECLARE_PLUGIN(BELLE_2009_I810744);
92
93}