1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief D0 -> K- mu+ nu_mu
 9  class BESIII_2018_I1697371 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1697371);
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_K, 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
45    /// Perform the per-event analysis
46    void analyze(const Event& event) {
47
48      // Loop over D0 mesons
49      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::D0)) {
50        if(isSemileptonicDecay(p, {PID::KMINUS, PID::ANTIMUON, PID::NU_MU})) {
51          _h_q2_K ->fill(q2(p, PID::KMINUS));
52        }
53      }
54    }
55
56
57    /// Normalise histograms etc., after the run
58    void finalize() {
59      normalize(_h_q2_K);
60    }
61
62    /// @}
63
64
65    /// @name Histograms
66    /// @{
67    Histo1DPtr _h_q2_K;
68    /// @}
69
70
71  };
72
73
74  RIVET_DECLARE_PLUGIN(BESIII_2018_I1697371);
75
76}