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BESIII_2020_I1771616

Dalitz plot analysis of $\psi(2S)\to K^+K^-\eta$
Experiment: BESIII (BEPC)
Inspire ID: 1771616
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 101 (2020) 3, 032008
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing psi(2S) originally e+e-

Measurement of the mass distributions in the decay $\psi(2S)\to K^+K^-\eta$. The data were read from the plots in the paper. 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_2020_I1771616.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 psi(2S) -> K+K- eta
10  class BESIII_2020_I1771616 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1771616);
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==100443);
23      declare(ufs, "UFS");
24      DecayedParticles psi2S(ufs);
25      psi2S.addStable(PID::PI0);
26      psi2S.addStable(PID::K0S);
27      psi2S.addStable(PID::ETA);
28      psi2S.addStable(PID::ETAPRIME);
29      declare(psi2S, "psi2S");
30      for(unsigned int ix=0;ix<3;++ix)
31	book(_h[ix],1,1,1+ix);
32      book(_dalitz, "dalitz",50,0.,11.,50,0.0,11.);
33    }
34
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      static const map<PdgId,unsigned int> & mode   = { { 321,1}, {-321,1}, { 221,1} };
39      DecayedParticles psi2S = apply<DecayedParticles>(event, "psi2S");
40      // loop over particles
41      for(unsigned int ix=0;ix<psi2S.decaying().size();++ix) {
42	if(!psi2S.modeMatches(ix,3,mode)) continue;
43	const Particles & eta = psi2S.decayProducts()[ix].at( 221);
44	const Particles & Kp  = psi2S.decayProducts()[ix].at( 321);
45	const Particles & Km  = psi2S.decayProducts()[ix].at(-321);
46	double mminus = (Km[0].momentum()+eta[0].momentum()).mass2();
47	double mplus  = (Kp[0].momentum()+eta[0].momentum()).mass2();
48	double mneut  = (Kp[0].momentum()+Km [0].momentum()).mass2();
49	_h[0]->fill(sqrt(mneut ));
50	_h[1]->fill(sqrt(mplus ));
51	_h[2]->fill(sqrt(mminus));
52	_dalitz->fill(mplus,mminus);
53      }
54    }
55
56
57    /// Normalise histograms etc., after the run
58    void finalize() {
59      for(unsigned int ix=0;ix<3;++ix)
60	normalize(_h[ix]);
61      normalize(_dalitz);
62    }
63
64    /// @}
65
66
67    /// @name Histograms
68    /// @{
69    Histo1DPtr _h[3];
70    Histo2DPtr _dalitz;
71    /// @}
72
73
74  };
75
76
77  RIVET_DECLARE_PLUGIN(BESIII_2020_I1771616);
78
79}