Rivet analyses referenceBESIII_2015_I1391138Exclusive $D^0\to K^-,\pi^-e^+\nu_e$ decaysExperiment: BESIII (BEPC) Inspire ID: 1391138 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Differential decay rates for semileptonic $D^0\to K^-,\pi^-e^+\nu_e$ decays Source code: BESIII_2015_I1391138.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief Exclusive $D^0\to K^-,\pi^-e^+\nu_e$ decays
9 class BESIII_2015_I1391138 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2015_I1391138);
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_K, 1, 1, 3);
27 book(_h_q2_pi, 2, 1, 3);
28 book(nD0, "TMP/DCounter");
29 }
30
31
32 // Calculate the Q2 using mother and daugher meson
33 size_t q2(const Particle& B, int mesonID, size_t species) const {
34 FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
35 return axes[species].index(q*q) - 1;
36 }
37
38
39 // Check for explicit decay into pdgids
40 bool isSemileptonicDecay(const Particle& mother, vector<int> ids) const {
41 // Trivial check to ignore any other decays but the one in question modulo photons
42 const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
43 if (children.size()!=ids.size()) return false;
44 // Check for the explicit decay
45 return all(ids, [&](int i){return count(children, hasPID(i))==1;});
46 }
47
48
49 /// Perform the per-event analysis
50 void analyze(const Event& event) {
51
52 if (edges_K.empty()) edges_K = _h_q2_K->xEdges();
53 if (edges_pi.empty()) edges_pi = _h_q2_pi->xEdges();
54
55 // Loop over D0 mesons
56 for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::D0)) {
57 nD0->fill();
58 if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})) {
59 _h_q2_pi->fill( edges_pi[q2(p, PID::PIMINUS, 1)] );
60 }
61 else if (isSemileptonicDecay(p, {PID::KMINUS, PID::POSITRON, PID::NU_E})) {
62 _h_q2_K ->fill( edges_K[q2(p, PID::KMINUS, 0)] );
63 }
64 }
65 }
66
67
68 /// Normalise histograms etc., after the run
69 void finalize() {
70 // scale by D0 lifetime = 410.1e-6 ps (from PDG 2014 used in paper)
71 // and bin width 0.1 K and 0.2 pi
72 scale(_h_q2_K , 1./dbl(*nD0)/410.1e-6*0.1);
73 scale(_h_q2_pi, 1./dbl(*nD0)/410.1e-6*0.2);
74 }
75
76 /// @}
77
78
79 /// @name Histograms
80 /// @{
81 BinnedHistoPtr<string> _h_q2_K, _h_q2_pi;
82 CounterPtr nD0;
83 vector<string> edges_K, edges_pi;
84 YODA::Axis<double> axes[2] = { YODA::Axis<double>(17, 0.0, 1.7),
85 YODA::Axis<double>(13, 0.0, 2.6) };
86 /// @}
87
88 };
89
90
91 RIVET_DECLARE_PLUGIN(BESIII_2015_I1391138);
92
93}
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