1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief  B0 -> pi - l+ nu_l
 9  class BELLE_2022_I2163247 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2163247);
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(Cuts::pid==PID::B0), "UFS");
24      // histograms
25      for(unsigned int ix=0;ix<3;++ix) book(_h[ix],1,1,1+ix);
26      book(_nB,"TMP/nb");
27    }
28
29    // Calculate the Q2 using mother and daugher meson
30    double q2(const Particle& B, int mesonID) {
31      FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
32      return q*q;
33    }
34
35    // Check for explicit decay into pdgids
36    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
37      // Trivial check to ignore any other decays but the one in question modulo photons
38      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
39      if (children.size()!=ids.size()) return false;
40      // Check for the explicit decay
41      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
42    }
43
44
45    /// Perform the per-event analysis
46    void analyze(const Event& event) {
47      // Loop over B0 mesons 
48      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
49	_nB->fill();
50        if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})) {
51	  double qq = q2(p, PID::PIMINUS);
52	  _h[0]->fill(qq);
53	  _h[2]->fill(qq);
54	}
55	else if(isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
56	  double qq = q2(p, PID::PIMINUS);
57	  _h[1]->fill(qq);
58	  _h[2]->fill(qq);
59        }
60      }
61    }
62
63
64    /// Normalise histograms etc., after the run
65    void finalize() {
66      for(unsigned int ix=0;ix<3;++ix) {
67	double fact = 1e4;
68	if(ix==2) fact /=2;
69	scale(_h[ix], fact/ *_nB);
70      }
71    }
72
73    /// @}
74
75
76    /// @name Histograms
77    /// @{
78    Histo1DPtr _h[3];
79    CounterPtr _nB;
80    /// @}
81
82
83  };
84
85
86  RIVET_DECLARE_PLUGIN(BELLE_2022_I2163247);
87
88}