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 -> p pbar eta
10  class BES_2001_I556330 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BES_2001_I556330);
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+ix,1,1);
32      book(_dalitz, "dalitz",50,2.,5.,50,2.,5.);
33    }
34
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      static const map<PdgId,unsigned int> & mode   = { { 2212,1}, {-2212,1}, { 221,1} };
39      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
40      // loop over particles
41      for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
42	if(!psi.modeMatches(ix,3,mode)) continue;
43	const Particles & eta  = psi.decayProducts()[ix].at( 221);
44	const Particles & pp   = psi.decayProducts()[ix].at( 2212);
45	const Particles & pbar = psi.decayProducts()[ix].at(-2212);
46	double mminus = (pbar[0].momentum()+eta[0].momentum()).mass2();
47	double mplus  = (pp  [0].momentum()+eta[0].momentum()).mass2();
48	_h[0]->fill(sqrt(mplus ));
49	_h[0]->fill(sqrt(mminus));
50	_h[1]->fill((pp  [0].momentum()+pbar[0].momentum()).mass());
51	_dalitz->fill(mplus,mminus);
52      }
53    }
54
55
56    /// Normalise histograms etc., after the run
57    void finalize() {
58      normalize(_dalitz);
59      for(unsigned int ix=0;ix<2;++ix)
60	normalize(_h[ix]);
61    }
62
63    /// @}
64
65
66    /// @name Histograms
67    /// @{
68    Histo1DPtr _h[2];
69    Histo2DPtr _dalitz;
70    /// @}
71
72
73  };
74
75
76  RIVET_DECLARE_PLUGIN(BES_2001_I556330);
77
78}