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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 Based on BABAR_2015_I1334693
 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    // Calculate the Q2 using mother and daugher meson
32    double q2(const Particle& B, int mesonID) {
33      FourMomentum q = B.mom() - filter_select(B.children(), Cuts::pid==mesonID)[0];
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
49      // Loop over D0 mesons
50      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::D0)) {
51	nD0->fill();
52        if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})) {
53          _h_q2_pi->fill(q2(p, PID::PIMINUS));
54        }
55	else if(isSemileptonicDecay(p, {PID::KMINUS, PID::POSITRON, PID::NU_E})) {
56          _h_q2_K ->fill(q2(p, PID::KMINUS));
57        }
58      }
59    }
60
61    /// Normalise histograms etc., after the run
62    void finalize() {
63      // scale by D0 lifetime = 410.1e-6 ps (from PDG 2014 used in paper)
64      // and bin width 0.1 K and 0.2 pi
65      scale(_h_q2_K , 1./nD0->sumW()/410.1e-6*0.1);
66      scale(_h_q2_pi, 1./nD0->sumW()/410.1e-6*0.2);
67    }
68    //@}
69
70
71    /// @name Histograms
72    //@{
73    Histo1DPtr _h_q2_K,_h_q2_pi;
74    CounterPtr nD0;
75    //@}
76
77
78  };
79
80
81  // The hook for the plugin system
82  RIVET_DECLARE_PLUGIN(BESIII_2015_I1391138);
83
84
85}