1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief psi(2S) -> J/psi pi+pi-
 9  class MARKII_1979_I144382 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1979_I144382);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21
22      // Initialise and register projections
23      declare(UnstableParticles(Cuts::pid==100443),"UFS");
24      for(unsigned int ix=0;ix<2;++ix)
25	book(_h[ix], 1+ix, 1, 1);
26    }
27
28
29    void findDecayProducts(const Particle & mother, unsigned int & nstable,
30                           Particles& pip, Particles& pim, Particles & onium) {
31      for (const Particle& p : mother.children()) {
32        int id = p.pid();
33      	if (id == PID::PIMINUS) {
34          pim.push_back(p);
35          ++nstable;
36        }
37       	else if (id == PID::PIPLUS) {
38       	  pip.push_back(p);
39       	  ++nstable;
40       	}
41        else if (id==443) {
42          onium.push_back(p);
43          ++nstable;
44        }
45        else if ( !p.children().empty() ) {
46          findDecayProducts(p,nstable,pip,pim,onium);
47        }
48        else {
49          ++nstable;
50        }
51      }
52    }
53
54    /// Perform the per-event analysis
55    void analyze(const Event& event) {
56      // loop over unstable particles
57      for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles()) {
58      	unsigned int nstable(0);
59      	Particles pip, pim, onium;
60      	findDecayProducts(ups,nstable,pip,pim,onium);
61      	// check for onium
62      	if (onium.size() !=1 || nstable !=3 || pip.size()!=1 || pim.size() !=1) continue;
63      	double mpipi = (pip[0].momentum()+pim[0].momentum()).mass();
64      	_h[0]->fill(sqr(mpipi));
65	double mpi = 2.*pip[0].mass();
66	double x = (mpipi-mpi)/(ups.mass()-onium[0].mass()-mpi);
67	_h[1]->fill(x);
68      }
69    }
70
71
72    /// Normalise histograms etc., after the run
73    void finalize() {
74      for(unsigned int ix=0;ix<2;++ix)
75	normalize(_h[ix],1.,false);
76    }
77
78    /// @}
79
80
81    /// @name Histograms
82    /// @{
83    Histo1DPtr _h[2];
84    /// @}
85
86
87  };
88
89
90  RIVET_DECLARE_PLUGIN(MARKII_1979_I144382);
91
92}