1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief chi_c1 in Upsilon(1,2S) decays
 9  class BELLE_2017_I1499706 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2017_I1499706);
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 || Cuts::pid==100553), "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(_c[ix],"TMP/nUps"+toString(ix+1));
28      }
29    }
30
31   /// Recursively walk the decay tree to find decay products of @a p
32    void findDecayProducts(Particle mother, Particles& unstable) {
33      for(const Particle & p: mother.children()) {
34        const int id = abs(p.pid());
35	if(id == 20443) {
36	  unstable.push_back(p);
37	}
38	if(!p.children().empty())
39	  findDecayProducts(p, unstable);
40      }
41    }
42
43    /// Perform the per-event analysis
44    void analyze(const Event& event) {
45      // Find the Upsilons among the unstables
46      for(const Particle & ups : apply<UnstableParticles>(event, "UFS").particles()) {
47	unsigned int iloc = ups.pid()/100000;
48	_c[iloc]->fill();
49	// boost to rest frame
50	LorentzTransform boost;
51	if (ups.p3().mod() > 1*MeV)
52	  boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
53	// find ch_c1
54	Particles unstable;
55	findDecayProducts(ups,unstable);
56	// loop over chi_c1
57	for(const Particle& chi : unstable) {
58	  double Pmax = 0.5*(sqr(ups.mass())-sqr(chi.mass()))/ups.mass();
59	  const FourMomentum p2 = boost.transform(chi.momentum());
60	  const double xP = p2.p3().mod()/Pmax;
61	  _h[0][iloc]->fill(xP);
62	  _h[1][iloc]->fill(xP);
63	}
64      }
65    }
66
67
68    /// Normalise histograms etc., after the run
69    void finalize() {
70      for(unsigned int ix=0;ix<2;++ix)
71	for(unsigned int iy=0;iy<2;++iy)
72	  scale(_h[ix][iy],1e4/ *_c[iy]);
73    }
74
75    /// @}
76
77
78    /// @name Histograms
79    /// @{
80    Histo1DPtr _h[2][2];
81    CounterPtr _c[2];
82    /// @}
83
84
85  };
86
87
88  RIVET_DECLARE_PLUGIN(BELLE_2017_I1499706);
89
90}