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 psi(2S) -> J/psi pi+ pi-
10  class BESII_2007_I728304 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2007_I728304);
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::pid==100443);
24      declare(ufs, "UFS");
25      DecayedParticles psi(ufs);
26      psi.addStable(PID::PI0);
27      psi.addStable(PID::JPSI);
28      declare(psi, "psi");
29      // histos
30      for (unsigned int ix=0; ix<3; ++ix) {
31        book(_h[ix],1,1,1+ix);
32      }
33    }
34
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
39      // loop over particles
40      for (unsigned int ix=0; ix<psi.decaying().size(); ++ix) {
41        if (!psi.modeMatches(ix,3,mode)) continue;
42        const Particle & pip = psi.decayProducts()[ix].at( 211)[0];
43        const Particle & pim = psi.decayProducts()[ix].at(-211)[0];
44        FourMomentum pSigma = pip.momentum()+pim.momentum();
45        _h[0]->fill(pSigma.mass()/GeV);
46        const double cSigma = pSigma.z()/pSigma.p3().mod();
47        _h[1]->fill(cSigma);
48        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(pSigma.betaVec());
49        FourMomentum ppip = boost.transform(pip.momentum());
50        const double cPi=pSigma.p3().unit().dot(ppip.p3().unit());
51        _h[2]->fill(cPi);
52      }
53    }
54
55
56    /// Normalise histograms etc., after the run
57    void finalize() {
58      normalize(_h, 1.0, false);
59    }
60
61    /// @}
62
63
64    /// @name Histograms
65    /// @{
66    Histo1DPtr _h[3];
67    const map<PdgId,unsigned int> mode = { { 211,1}, {-211,1}, { 443,1} };
68    /// @}
69
70
71  };
72
73
74  RIVET_DECLARE_PLUGIN(BESII_2007_I728304);
75
76}