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 chi_cJ -> Lambda Lambdabar0 eta
10  class BESIII_2022_I2166668 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2166668);
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==10441 or
23						Cuts::pid==20443 or
24						Cuts::pid==445);
25      declare(ufs, "UFS");
26      DecayedParticles chi(ufs);
27      chi.addStable( PID::ETA);
28      chi.addStable( PID::LAMBDA);
29      chi.addStable(-PID::LAMBDA);
30      declare(chi, "chi");
31      // histos
32      for(unsigned int ix=0;ix<3;++ix)
33	book(_h[ix],1,1,1+ix);
34    }
35
36
37    /// Perform the per-event analysis
38    void analyze(const Event& event) {
39      static const map<PdgId,unsigned int> & mode = { { 3122,1}, {-3122,1}, { 221,1} };
40      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
41      for(unsigned int ix=0;ix<chi.decaying().size();++ix) {
42	if(!chi.modeMatches(ix,3,mode)) continue;
43	const Particle & lam = chi.decayProducts()[ix].at( 3122)[0];
44	const Particle & lamb = chi.decayProducts()[ix].at(-3122)[0];
45	const Particle & eta  = chi.decayProducts()[ix].at(  221)[0];
46	_h[0]->fill((lam .momentum()+lamb.momentum()).mass());
47	_h[1]->fill((lam .momentum()+eta .momentum()).mass());
48	_h[2]->fill((lamb.momentum()+eta .momentum()).mass());
49      }
50    }
51
52
53    /// Normalise histograms etc., after the run
54    void finalize() {
55      for(unsigned int ix=0;ix<3;++ix)
56	normalize(_h[ix],1.,false);
57    }
58
59    /// @}
60
61
62    /// @name Histograms
63    /// @{
64    Histo1DPtr _h[3];
65    /// @}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(BESIII_2022_I2166668);
72
73}