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 -> pbar Sigma+ K0S
10  class BESIII_2023_I2721091 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2721091);
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( 3222);
28      psi.addStable(-3222);
29      declare(psi, "psi");
30      for (unsigned int iy=0; iy<3; ++iy)
31        book(_h[iy], 1, 1, 1+iy);
32    }
33
34
35    /// Perform the per-event analysis
36    void analyze(const Event& event) {
37      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
38      // loop over particles
39      for (unsigned int ix=0;ix<psi.decaying().size();++ix) {
40        int isign=1;
41       	if     (psi.modeMatches(ix,3,mode1)) isign =  1;
42        else if(psi.modeMatches(ix,3,mode2)) isign = -1;
43        else continue;
44       	const Particle& k0   = psi.decayProducts()[ix].at( 310       )[0];
45       	const Particle& sigp = psi.decayProducts()[ix].at( isign*3222)[0];
46       	const Particle& prot = psi.decayProducts()[ix].at(-isign*2212)[0];
47        _h[0]->fill((prot.mom()+k0  .mom()).mass());
48        _h[1]->fill((sigp.mom()+k0  .mom()).mass());
49        _h[2]->fill((sigp.mom()+prot.mom()).mass());
50      }
51    }
52
53
54    /// Normalise histograms etc., after the run
55    void finalize() {
56      normalize(_h);
57    }
58
59    /// @}
60
61
62    /// @name Histograms
63    /// @{
64    Histo1DPtr _h[3];
65    const map<PdgId,unsigned int> mode1 = { {-2212,1}, { 3222,1}, { 310,1} };
66    const map<PdgId,unsigned int> mode2 = { { 2212,1}, {-3222,1}, { 310,1} };
67    /// @}
68
69
70  };
71
72
73  RIVET_DECLARE_PLUGIN(BESIII_2023_I2721091);
74
75}