1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief q^2 in D0 -> pi- mu+ nu_mu and D+ -> pi0  mu+ nu_mu decays
 9  class BESIII_2018_I1655158 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1655158);
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_D0, 1, 1, 1);
27      book(_h_q2_Dp, 2, 1, 1);
28    }
29
30    // Calculate the Q2 using mother and daugher meson
31    double q2(const Particle& B, int mesonID) {
32      FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
33      return q*q;
34    }
35
36    // Check for explicit decay into pdgids
37    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
38      // Trivial check to ignore any other decays but the one in question modulo photons
39      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
40      if (children.size()!=ids.size()) return false;
41      // Check for the explicit decay
42      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
43    }
44
45    /// Perform the per-event analysis
46    void analyze(const Event& event) {
47      // Loop over D mesons
48      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::D0 or
49                                                                               Cuts::pid==PID::DPLUS )) {
50        if (p.pid()==PID::D0 &&
51            isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU}) ) {
52          _h_q2_D0->fill(q2(p, PID::PIMINUS));
53        }
54        else if(p.pid()==PID::DPLUS &&
55                isSemileptonicDecay(p, {PID::PI0, PID::ANTIMUON, PID::NU_MU}) ) {
56          _h_q2_Dp->fill(q2(p, PID::PI0));
57        }
58      }
59    }
60
61
62    /// Normalise histograms etc., after the run
63    void finalize() {
64      normalize(_h_q2_D0, 1.);
65      normalize(_h_q2_Dp, 1.);
66    }
67
68    /// @}
69
70
71    /// @name Histograms
72    /// @{
73    Histo1DPtr _h_q2_D0, _h_q2_Dp;
74    /// @}
75
76
77  };
78
79
80  RIVET_DECLARE_PLUGIN(BESIII_2018_I1655158);
81
82
83}