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BESIII_2015_I1391138

Exclusive $D^0\to K^-,\pi^-e^+\nu_e$ decays
Experiment: BESIII (BEPC)
Inspire ID: 1391138
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D92 (2015) 072012, 2015
Beams: * *
Beam energies: ANY
Run details:
  • Events with D-decays, either particle guns or collisions.

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}