rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BABAR_2013_I1116411

Exclusive semileptonic Bplus to omega decays.
Experiment: BABAR (PEP-II)
Inspire ID: 1116411
Status: VALIDATED
Authors:
  • Holger Schulz
No references listed
Beams: * *
Beam energies: ANY
Run details:
  • Events with B-decays, either particle guns or collisions.

Implementation of Lorentz invariant q2 distributions ("form factor") for semileptonic Bplus decays

Source code: BABAR_2013_I1116411.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Add a short analysis description here
 9  class BABAR_2013_I1116411 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2013_I1116411);
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    
30    // Calculate the Q2 using mother and daughter charged lepton
31    double q2(const Particle& B) {
32      const Particle chlept = filter_select(B.children(), Cuts::pid==PID::POSITRON || Cuts::pid==PID::ANTIMUON)[0];
33      FourMomentum q = B.mom() - chlept.mom();
34      return q*q;
35    }
36
37    // Check for explicit decay into pdgids
38    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
39      // Trivial check to ignore any other decays but the one in question modulo photons
40      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
41      if (children.size()!=ids.size()) return false;
42      // Check for the explicit decay
43      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
44    }
45
46    /// Perform the per-event analysis
47    void analyze(const Event& event) {
48      // Get B+ Mesons
49      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::BPLUS)) {
50        if (isSemileptonicDecay(p, {PID::OMEGA, PID::POSITRON, PID::NU_E}) ||
51            isSemileptonicDecay(p, {PID::OMEGA, PID::ANTIMUON, PID::NU_MU})) {
52            _h_q2->fill(q2(p));
53        }
54      }
55    }
56
57
58    /// Normalise histograms etc., after the run
59    void finalize() {
60
61      normalize(_h_q2, 1.21); // normalize to BF
62
63    }
64
65    //@}
66
67
68  private:
69
70
71    /// @name Histograms
72    //@{
73    Histo1DPtr _h_q2;
74    //@}
75
76
77  };
78
79
80  // The hook for the plugin system
81  RIVET_DECLARE_PLUGIN(BABAR_2013_I1116411);
82
83
84}