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 -> KS0 phi
10  class ARGUS_1987_I247005 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I247005);
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::PHI);
29      declare(D0, "D0");
30      // histos
31      book(_h,1,1,1);
32    }
33
34
35    /// Perform the per-event analysis
36    void analyze(const Event& event) {
37      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
38      // loop over particles
39      for (unsigned int ix=0; ix<D0.decaying().size(); ++ix) {
40        if (!D0.modeMatches(ix,2,mode)) continue;
41        //const Particle & K0  = D0.decayProducts()[ix].at(310)[0];
42        const Particle& phi = D0.decayProducts()[ix].at(333)[0];
43        if (phi.children().size()!=2) continue;
44        if (phi.children()[0].abspid()!=PID::KPLUS ||
45            phi.children()[1].abspid()!=PID::KPLUS ) continue;
46        // first boost all relevant momenta to D0 rest frame
47        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(D0.decaying()[ix].mom());
48        FourMomentum pphi = boost.transform(phi.mom());
49        FourMomentum pK   = boost.transform(phi.children()[0].mom());
50        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pphi.betaVec());
51        Vector3 axis1 = pphi.p3().unit();
52        Vector3 axis2 = boost2.transform(pK ).p3().unit();
53        _h->fill(axis1.dot(axis2));
54      }
55    }
56
57
58    /// Normalise histograms etc., after the run
59    void finalize() {
60      normalize(_h, 1.0, false);
61    }
62
63    /// @}
64
65
66    /// @name Histograms
67    /// @{
68    Histo1DPtr _h;
69    const map<PdgId,unsigned int> mode = { { 310,1}, { 333,1}};
70    /// @}
71
72
73  };
74
75
76  RIVET_DECLARE_PLUGIN(ARGUS_1987_I247005);
77
78}