Rivet analyses referenceBESIII_2017_I1621266Dalitz plot analysis of $J/\psi$ and $\psi(2S)\to\pi^+\pi^-\eta^\prime$Experiment: BESIII (BEPC) Inspire ID: 1621266 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the mass distributions in the decays $J/\psi$ and $\psi(2S)\to\pi^+\pi^-\eta^\prime$ by BESIII. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. Also the sideband background from the plots has been subtracted. It is also not clear that any resolution effects have been unfolded. Source code: BESIII_2017_I1621266.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$ and psi(2S) to pi+ pi- eta'
10 class BESIII_2017_I1621266 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1621266);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 UnstableParticles ufs = UnstableParticles(Cuts::pid== 443 || Cuts::pid==100443);
24 declare(ufs, "UFS");
25 DecayedParticles PSI(ufs);
26 PSI.addStable(PID::ETAPRIME);
27 declare(PSI,"PSI");
28 // histos
29 book(_h_pipi [0],1,1,1);
30 book(_h_pieta[0],1,1,2);
31 book(_h_pipi [1],1,1,3);
32 book(_h_pieta[1],1,1,4);
33 book(_dalitz[0], "dalitz_Jpsi" ,50,1., 9.,50,1., 9.);
34 book(_dalitz[1], "dalitz_psi2S",50,1.,14.,50,1.,14.);
35 }
36
37 /// Perform the per-event analysis
38 void analyze(const Event& event) {
39 static const map<PdgId,unsigned int> & mode = { { 211,1},{-211,1}, {331,1}};
40 DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
41 // loop over particles
42 for(unsigned int ix=0;ix<PSI.decaying().size();++ix) {
43 if (!PSI.modeMatches(ix,3,mode)) continue;
44 const Particle & pip = PSI.decayProducts()[ix].at( 211)[0];
45 const Particle & pim = PSI.decayProducts()[ix].at(-211)[0];
46 const Particle & eta = PSI.decayProducts()[ix].at( 331)[0];
47 unsigned int iloc = PSI.decaying()[ix].pid()/100000;
48 double mminus = (pim.momentum()+eta.momentum()).mass2();
49 double mplus = (pip.momentum()+eta.momentum()).mass2();
50 double mneut = (pip.momentum()+pim.momentum()).mass2();
51 _h_pipi[iloc] ->fill(sqrt(mneut ));
52 _h_pieta[iloc]->fill(sqrt(mplus ));
53 //_h_pieta[iloc]->fill(sqrt(mminus));
54 _dalitz[iloc]->fill(mplus,mminus);
55 }
56 }
57
58
59 /// Normalise histograms etc., after the run
60 void finalize() {
61 for(unsigned int ix=0;ix<2;++ix) {
62 normalize(_h_pipi [ix]);
63 normalize(_h_pieta[ix]);
64 normalize(_dalitz [ix]);
65 }
66 }
67
68 /// @}
69
70
71 /// @name Histograms
72 /// @{
73 Histo1DPtr _h_pipi[2],_h_pieta[2];
74 Histo2DPtr _dalitz[2];
75 /// @}
76
77
78 };
79
80
81 RIVET_DECLARE_PLUGIN(BESIII_2017_I1621266);
82
83}
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