1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4#include "Rivet/Projections/DecayedParticles.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// @brief B0 -> K+ K- KS0
10  class BELLE_2010_I862241 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2010_I862241);
15
16
17    /// @name Analysis methods
18    /// @{
19
20    /// Book histograms and initialise projections before the run
21    void init() {
22      // Initialise and register projections
23      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
24      declare(ufs, "UFS");
25      DecayedParticles B0(ufs);
26      B0.addStable(PID::K0S);
27      declare(B0, "B0");
28      // histograms
29      for(unsigned int ix=0;ix<4;++ix)
30	book(_h[ix],1,1,1+ix);
31    }
32
33
34    /// Perform the per-event analysis
35    void analyze(const Event& event) {
36      static const map<PdgId,unsigned int> & mode = { { 321,1}, {-321,1}, { 310,1}};
37      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
38      // loop over particles
39      for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
40	if (!B0.modeMatches(ix,3,mode)) continue;
41	int sign = B0.decaying()[ix].pid()>0 ? 1 : -1;
42      	const Particle & Kp  = B0.decayProducts()[ix].at( 321*sign)[0];
43      	const Particle & Km  = B0.decayProducts()[ix].at(-321*sign)[0];
44      	const Particle & K0  = B0.decayProducts()[ix].at( 310     )[0];
45	_h[0]->fill((K0.momentum()+Kp.momentum()).mass());
46	_h[1]->fill((K0.momentum()+Km.momentum()).mass());
47	_h[2]->fill((Km.momentum()+Kp.momentum()).mass());
48	_h[3]->fill((Km.momentum()+Kp.momentum()).mass());
49      }
50    }
51
52
53    /// Normalise histograms etc., after the run
54    void finalize() {
55      for(unsigned int ix=0;ix<4;++ix)
56	normalize(_h[ix],1.);
57    }
58
59    /// @}
60
61
62    /// @name Histograms
63    /// @{
64    Histo1DPtr _h[4];
65    /// @}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(BELLE_2010_I862241);
72
73}