1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief B -> D semileptonic
 9  class BELLE_2022_I2169621 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2169621);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // projection
22      declare(UnstableParticles(Cuts::pid==511 or
23      				Cuts::pid==521), "UFS");
24      // histograms
25      for(unsigned int ix=0;ix<4;++ix)
26      	book(_h[ix],1,1,1+ix);
27      for(unsigned int ix=0;ix<2;++ix)
28      	book(_nB[ix],"TMP/nB_"+toString(ix));
29    }
30
31    // Check for explicit decay into pdgids
32    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
33      // Trivial check to ignore any other decays but the one in question modulo photons
34      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
35      if (children.size()!=ids.size()) return false;
36      // Check for the explicit decay
37      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
38    }
39
40    // Calculate the recoil w using mother and daugher meson
41    double recoilW(const Particle& B, int mesonID) {
42      // TODO why does that not work with const?
43      Particle D = select(B.children(), Cuts::pid==mesonID)[0];
44      FourMomentum q = B.mom() - D.mom();
45      return (B.mom()*B.mom() + D.mom()*D.mom() - q*q )/ (2. * sqrt(B.mom()*B.mom()) * sqrt(D.mom()*D.mom()) );
46    }
47
48    /// Perform the per-event analysis
49    void analyze(const Event& event) {
50      for(const Particle & p : apply<UnstableParticles>(event, "UFS").particles()) {
51      	if(p.children().size()<=1) continue;
52      	if(p.pid()==PID::BPLUS) {
53      	  _nB[0]->fill();
54      	  if (isSemileptonicDecay(p, {PID::D0BAR,PID::POSITRON,PID::NU_E}))  _h[0]->fill(recoilW(p, PID::D0BAR));
55      	  if (isSemileptonicDecay(p, {PID::D0BAR,PID::ANTIMUON,PID::NU_MU})) _h[1]->fill(recoilW(p, PID::D0BAR));
56      	}
57      	else if(p.pid()==PID::B0) {
58      	  _nB[1]->fill();
59      	  if (isSemileptonicDecay(p, {PID::DMINUS,PID::POSITRON,PID::NU_E}))  _h[2]->fill(recoilW(p, PID::DMINUS));
60      	  if (isSemileptonicDecay(p, {PID::DMINUS,PID::ANTIMUON,PID::NU_MU})) _h[3]->fill(recoilW(p, PID::DMINUS));
61      	}
62      }
63    }
64
65
66    /// Normalise histograms etc., after the run
67    void finalize() {
68      double tau[2] = {1638e-15,1519e-15};
69      double hbar = 6.582119569e-10;
70      for(unsigned int ix=0;ix<4;++ix) {
71      	double fact = ix<2 ? hbar/tau[0] : hbar/tau[1];
72      	CounterPtr c = ix<2 ? _nB[0] : _nB[1];
73      	scale(_h[ix],fact/ *c);
74      }
75    }
76
77    /// @}
78
79
80    /// @name Histograms
81    /// @{
82    Histo1DPtr _h[4];
83    CounterPtr _nB[2];
84    /// @}
85
86
87  };
88
89
90  RIVET_DECLARE_PLUGIN(BELLE_2022_I2169621);
91
92}