1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief J/psi and psi(2S) in Upsilon(1S) decays
 9  class BELLE_2016_I1454405 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2016_I1454405);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Initialise and register projections
22      declare(UnstableParticles(Cuts::pid==553), "UFS");
23      //histos
24      for(unsigned int ix=0;ix<2;++ix)
25	for(unsigned int iy=0;iy<2;++iy)
26	  book(_h[ix][iy],1,1+ix,1+iy);
27      book(_nUps,"TMP/nUps");
28    }
29
30   /// Recursively walk the decay tree to find decay products of @a p
31    void findDecayProducts(Particle mother, Particles& unstable) {
32      for(const Particle & p: mother.children()) {
33        const int id = abs(p.pid());
34	if(id == 443 || id==100443) {
35	  unstable.push_back(p);
36	}
37	if(!p.children().empty())
38	  findDecayProducts(p, unstable);
39      }
40    }
41
42    /// Perform the per-event analysis
43    void analyze(const Event& event) {
44      // Find the Upsilons among the unstables
45      for(const Particle & ups : apply<UnstableParticles>(event, "UFS").particles()) {
46	_nUps->fill();
47	// boost to rest frame
48	LorentzTransform boost;
49	if (ups.p3().mod() > 1*MeV)
50	  boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
51	// find  psi/psi(2S)
52	Particles unstable;
53	findDecayProducts(ups,unstable);
54	// loop over psi/psi(2S)
55	for(const Particle& psi : unstable) {
56	  double Pmax = 0.5*(sqr(ups.mass())-sqr(psi.mass()))/ups.mass();
57	  const FourMomentum p2 = boost.transform(psi.momentum());
58	  const double xP = p2.p3().mod()/Pmax;
59	  if(psi.pid()==443) {
60	    _h[0][0]->fill(xP);
61	    _h[1][0]->fill(xP);
62	  }
63	  else {
64	    _h[0][1]->fill(xP);
65	    _h[1][1]->fill(xP);
66	  }
67	}
68      }
69    }
70
71
72    /// Normalise histograms etc., after the run
73    void finalize() {
74      for(unsigned int ix=0;ix<2;++ix)
75	for(unsigned int iy=0;iy<2;++iy)
76	  scale(_h[ix][iy],1e4/ *_nUps);
77    }
78
79    /// @}
80
81
82    /// @name Histograms
83    /// @{
84    Histo1DPtr _h[2][2];
85    CounterPtr _nUps;
86    /// @}
87
88
89  };
90
91
92  RIVET_DECLARE_PLUGIN(BELLE_2016_I1454405);
93
94}