rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BESIII_2022_I2016785

Radiative $J/\psi\to\gamma \eta^\prime\eta^\prime$
Experiment: BESIII (BEPC)
Inspire ID: 2016785
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 105 (2022) 7, 072002
Beams: * *
Beam energies: ANY
    No run details listed

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
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief J/psi -> gamma eta' eta'
  class BESIII_2022_I2016785 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2016785);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid==443);
      declare(ufs, "UFS");
      DecayedParticles psi(ufs);
      psi.addStable(PID::PI0);
      psi.addStable(PID::K0S);
      psi.addStable(PID::ETA);
      psi.addStable(PID::ETAPRIME);
      declare(psi, "psi");
      for(unsigned int ix=0;ix<2;++ix)
	    book(_h[ix],1,1,1+ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 331,2} ,{22,1} };
      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
      // loop over particles
      for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
	if(!psi.modeMatches(ix,3,mode)) continue;
	const Particles & eta   = psi.decayProducts()[ix].at( 331);
	const Particle & gamma  = psi.decayProducts()[ix].at(  22)[0];
	_h[0]->fill((eta[0].momentum()+eta[1].momentum()).mass());
	for(unsigned int ix=0;ix<2;++ix)
	  _h[1]->fill((gamma.momentum()+eta[ix].momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<2;++ix)
	normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2022_I2016785);

}