1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief  D -> eta semi-leptonic q^2
 9  class CLEOC_2011_I875526 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2011_I875526);
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      // histograms
25      book(_h_q2_Dp_eta_A,1,1,1);
26      book(_h_q2_Dp_eta_B,1,1,2);
27      book(_nDp,"TMP/nDp");
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::abspid==PID::DPLUS )) {
49	_nDp->fill();
50	if(isSemileptonicDecay(p, {PID::ETA, PID::POSITRON, PID::NU_E})  ||
51	   isSemileptonicDecay(p, {PID::ETA, PID::ELECTRON, PID::NU_EBAR})) {
52	  double q = q2(p, PID::ETA);
53	  _h_q2_Dp_eta_A->fill(q);
54	  _h_q2_Dp_eta_B->fill(q);
55	}
56      }
57    }
58
59
60    /// Normalise histograms etc., after the run
61    void finalize() {
62      scale(_h_q2_Dp_eta_A, 1./ *_nDp);
63      scale(_h_q2_Dp_eta_B, 1./ *_nDp);
64    }
65
66    /// @}
67
68
69    /// @name Histograms
70    /// @{
71    Histo1DPtr _h_q2_Dp_eta_A,_h_q2_Dp_eta_B;
72    CounterPtr _nD0,_nDp;
73    /// @}
74
75
76  };
77
78
79  RIVET_DECLARE_PLUGIN(CLEOC_2011_I875526);
80
81}