Rivet analyses referenceBELLE_2011_I878990Exclusive semileptonic $B^0\to\pi^-$ decays.Experiment: BELLE (KEKB) Inspire ID: 878990 Status: VALIDATED Authors:
Beams: * * Beam energies: ANY Run details:
Implementation of Lorentz invariant q2 distributions ("form factor") for semileptonic B0 decays Source code: BELLE_2011_I878990.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief q^2 in B0 -> pi- l+ nu_l decays
9 class BELLE_2011_I878990 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2011_I878990);
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 /// Perform the per-event analysis
45 void analyze(const Event& event) {
46 // Loop over B0 mesons
47 for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::B0)) {
48 if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E}) ||
49 isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
50 _h_q2->fill(q2(p, PID::PIMINUS));
51 }
52 }
53 }
54
55
56 /// Normalise histograms etc., after the run
57 void finalize() {
58
59 normalize(_h_q2, 3000.86); // normalize to BF*dQ2
60
61 }
62
63 /// @}
64
65
66 private:
67
68
69 /// @name Histograms
70 /// @{
71 Histo1DPtr _h_q2;
72 /// @}
73
74
75 };
76
77
78 RIVET_DECLARE_PLUGIN(BELLE_2011_I878990);
79
80
81}
|