Rivet analyses referenceBESIII_2018_I1662660$D^+\to \eta e^+\nu_e$ $q^2$ spectrumExperiment: BESIII (BEPC) Inspire ID: 1662660 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the $q^2$ spectrum in the decay $D^+\to \eta e^+\nu_e$ BES-III. Source code: BESIII_2018_I1662660.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief q^2 in D+ -> eta e+ nu_e
9 class BESIII_2018_I1662660 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1662660);
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() - filter_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 D+ mesons
47 for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::DPLUS )) {
48 if(p.pid()==PID::DPLUS && isSemileptonicDecay(p, {PID::ETA, PID::EPLUS, PID::NU_E}) ) {
49 _h_q2->fill(q2(p, PID::ETA));
50 }
51 }
52 }
53
54
55 /// Normalise histograms etc., after the run
56 void finalize() {
57 normalize(_h_q2);
58 }
59
60 ///@}
61
62
63 /// @name Histograms
64 ///@{
65 Histo1DPtr _h_q2;
66 ///@}
67
68
69 };
70
71
72 RIVET_DECLARE_PLUGIN(BESIII_2018_I1662660);
73
74}
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