1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief q^2 in B0 -> pi- l+ nu_l decays
 9  class BELLE_2011_I878990 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2011_I878990);
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(), "UFS");
24
25      // Book histograms
26      book(_h_q2 ,1, 1, 1);
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    /// Perform the per-event analysis
45    void analyze(const Event& event) {
46      // Loop over B0 mesons
47      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::B0)) {
48        if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E}) ||
49            isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
50            _h_q2->fill(q2(p, PID::PIMINUS));
51        }
52      }
53    }
54
55
56    /// Normalise histograms etc., after the run
57    void finalize() {
58
59      normalize(_h_q2, 3000.86); // normalize to BF*dQ2
60
61    }
62
63    /// @}
64
65
66  private:
67
68
69    /// @name Histograms
70    /// @{
71    Histo1DPtr _h_q2;
72    /// @}
73
74
75  };
76
77
78  RIVET_DECLARE_PLUGIN(BELLE_2011_I878990);
79
80
81}