1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Lambda_b0 -> Lambda_c+ semi-leptonic
 9  class LHCB_2017_I1621811 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2017_I1621811);
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
45    /// Perform the per-event analysis
46    void analyze(const Event& event) {
47      for (const Particle& p :  apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==5122)) {
48	if(p.pid()>0) {
49	  if(isSemileptonicDecay(p, {4122, PID::MUON, PID::NU_MUBAR})) {
50	    _h_q2->fill(q2(p, 4122));
51	  }
52	}
53	else {
54	  if(isSemileptonicDecay(p, {-4122, PID::ANTIMUON, PID::NU_MU})) {
55	    _h_q2->fill(q2(p, -4122));
56	  }
57	}
58      }
59    }
60
61
62    /// Normalise histograms etc., after the run
63    void finalize() {
64      // normalize to unity
65      normalize(_h_q2);
66    }
67
68    /// @}
69
70
71    /// @name Histograms
72    /// @{
73    Histo1DPtr _h_q2;
74    /// @}
75
76
77  };
78
79
80  RIVET_DECLARE_PLUGIN(LHCB_2017_I1621811);
81
82}