Rivet analyses referenceBESIII_2022_I2016785Radiative $J/\psi\to\gamma \eta^\prime\eta^\prime$Experiment: BESIII (BEPC) Inspire ID: 2016785 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY
Measurement of the mass distributions in the decay $J/\psi\to\gamma \eta^\prime\eta^\prime$. The data were read from the plots in the paper. It is also not clear that any resolution effects have been unfolded. Source code: BESIII_2022_I2016785.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief J/psi -> gamma eta' eta'
10 class BESIII_2022_I2016785 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2016785);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 UnstableParticles ufs = UnstableParticles(Cuts::pid==443);
23 declare(ufs, "UFS");
24 DecayedParticles psi(ufs);
25 psi.addStable(PID::PI0);
26 psi.addStable(PID::K0S);
27 psi.addStable(PID::ETA);
28 psi.addStable(PID::ETAPRIME);
29 declare(psi, "psi");
30 for(unsigned int ix=0;ix<2;++ix)
31 book(_h[ix],1,1,1+ix);
32 }
33
34
35 /// Perform the per-event analysis
36 void analyze(const Event& event) {
37 static const map<PdgId,unsigned int> & mode = { { 331,2} ,{22,1} };
38 DecayedParticles psi = apply<DecayedParticles>(event, "psi");
39 // loop over particles
40 for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
41 if(!psi.modeMatches(ix,3,mode)) continue;
42 const Particles & eta = psi.decayProducts()[ix].at( 331);
43 const Particle & gamma = psi.decayProducts()[ix].at( 22)[0];
44 _h[0]->fill((eta[0].momentum()+eta[1].momentum()).mass());
45 for(unsigned int ix=0;ix<2;++ix)
46 _h[1]->fill((gamma.momentum()+eta[ix].momentum()).mass());
47 }
48 }
49
50
51 /// Normalise histograms etc., after the run
52 void finalize() {
53 for(unsigned int ix=0;ix<2;++ix)
54 normalize(_h[ix],1.,false);
55 }
56
57 /// @}
58
59
60 /// @name Histograms
61 /// @{
62 Histo1DPtr _h[2];
63 /// @}
64
65
66 };
67
68
69 RIVET_DECLARE_PLUGIN(BESIII_2022_I2016785);
70
71}
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