Rivet analyses referenceBESIII_2022_I1997940EM Dalitz $J/\psi\to e^+e^- \eta^\prime\pi^+\pi^-$ decayExperiment: BESIII (BEPC) Inspire ID: 1997940 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the hadronic mass distribution in the decay $J/\psi\to e^+e^- \eta^\prime\pi^+\pi^-$. 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_I1997940.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 -> e+e- eta' pi+pi-
10 class BESIII_2022_I1997940 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I1997940);
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 = { { 211,1}, {-211,1}, { 331,1} ,{11,1}, {-11,1} };
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,5,mode)) continue;
42 const Particle & eta = psi.decayProducts()[ix].at( 331)[0];
43 const Particle & pip = psi.decayProducts()[ix].at( 211)[0];
44 const Particle & pim = psi.decayProducts()[ix].at(-211)[0];
45 double mass = (pip.momentum()+pim.momentum()+eta.momentum()).mass();
46 _h[0]->fill(mass);
47 _h[1]->fill(mass);
48 }
49 }
50
51
52 /// Normalise histograms etc., after the run
53 void finalize() {
54 for(unsigned int ix=0;ix<2;++ix)
55 normalize(_h[ix],1.,false);
56 }
57
58 /// @}
59
60
61 /// @name Histograms
62 /// @{
63 Histo1DPtr _h[2];
64 /// @}
65
66
67 };
68
69
70 RIVET_DECLARE_PLUGIN(BESIII_2022_I1997940);
71
72}
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