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 D0 -> eta pi+pi- decays
10  class CLEOC_2008_I779705 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2008_I779705);
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::abspid==421);
24      declare(ufs, "UFS");
25      DecayedParticles D0(ufs);
26      D0.addStable(PID::PI0);
27      D0.addStable(PID::K0S);
28      D0.addStable(PID::ETA);
29      D0.addStable(PID::ETAPRIME);
30      declare(D0, "D0");
31      // histograms
32      book(_h_eta_pi,1,1,1);
33      book(_h_pi_pi ,1,1,2);
34    }
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      static const map<PdgId,unsigned int> & mode   = { { 211,1},{-211,1}, {221,1}};
39      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
40      // loop over particles
41      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
42        if( !D0.modeMatches(ix,3,mode)  ) continue;
43        int sign = D0.decaying()[ix].pid()/421;
44        const Particles & eta = D0.decayProducts()[ix].at(221);
45        const Particles & pip = D0.decayProducts()[ix].at( sign*211);
46        const Particles & pim = D0.decayProducts()[ix].at(-sign*211);
47        _h_eta_pi->fill((pip[0].momentum()+eta[0].momentum()).mass());
48        _h_pi_pi ->fill((pip[0].momentum()+pim[0].momentum()).mass());
49      }
50    }
51
52
53    /// Normalise histograms etc., after the run
54    void finalize() {
55      normalize(_h_eta_pi);
56      normalize(_h_pi_pi );
57    }
58
59    /// @}
60
61
62    /// @name Histograms
63    /// @{
64    Histo1DPtr _h_eta_pi,_h_pi_pi;
65    /// @}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(CLEOC_2008_I779705);
72
73}