Rivet analyses referenceBESIII_2019_I1712742Semileptonic $D_s^+\to \eta e^+\nu_e$ and $\eta^\prime e^+\nu_e$ decaysExperiment: BESIII (BEPC) Inspire ID: 1712742 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Differential decay rates for semileptonic $D_s^+\to \eta e^+\nu_e$ and $\eta^\prime e^+\nu_e$ decays Source code: BESIII_2019_I1712742.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief D_s -> eta, eta' semi-leptonic
9 class BESIII_2019_I1712742 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1712742);
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 // histograms
25 for(unsigned int ix=0;ix<2;++ix)
26 for(unsigned int iy=0;iy<2;++iy)
27 book(_h[ix][iy],ix+1,1,iy+1);
28 // counter for normalization
29 book(_nDs, "TMP/nDs");
30 }
31
32 // Calculate the Q2 using mother and daugher meson
33 double q2(const Particle& B, int mesonID) {
34 FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
35 return q*q;
36 }
37
38 // Check for explicit decay into pdgids
39 bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
40 // Trivial check to ignore any other decays but the one in question modulo photons
41 const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
42 if (children.size()!=ids.size()) return false;
43 // Check for the explicit decay
44 return all(ids, [&](int i){return count(children, hasPID(i))==1;});
45 }
46
47 /// Perform the per-event analysis
48 void analyze(const Event& event) {
49 // Loop over Ds mesons
50 for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==431)) {
51 _nDs->fill();
52 if (isSemileptonicDecay(p, {PID::ETA, PID::POSITRON, PID::NU_E})) {
53 _h[0][0]->fill(q2(p, PID::ETA));
54 _h[0][1]->fill(q2(p, PID::ETA));
55 }
56 else if(isSemileptonicDecay(p, {PID::ETAPRIME, PID::POSITRON, PID::NU_E})) {
57 _h[1][0] ->fill(q2(p, PID::ETAPRIME));
58 _h[1][1] ->fill(q2(p, PID::ETAPRIME));
59 }
60 }
61 }
62
63
64 /// Normalise histograms etc., after the run
65 void finalize() {
66 // D_s lifetime pdg2018 (ns)
67 double tau = 504e-6;
68 for(unsigned int ix=0;ix<2;++ix)
69 for(unsigned int iy=0;iy<2;++iy)
70 scale(_h[ix][iy],1./tau/ *_nDs);
71 }
72
73 /// @}
74
75
76 /// @name Histograms
77 /// @{
78 CounterPtr _nDs;
79 Histo1DPtr _h[2][2];
80 /// @}
81
82
83 };
84
85
86 RIVET_DECLARE_PLUGIN(BESIII_2019_I1712742);
87
88}
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