1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/Beam.hh"
 4#include "Rivet/Projections/FinalState.hh"
 5#include "Rivet/Projections/ChargedFinalState.hh"
 6#include "Rivet/Projections/UnstableParticles.hh"
 7
 8namespace Rivet {
 9
10
11  /// @brief OPAL K0 fragmentation function paper
12  ///
13  /// @author Peter Richardson
14  class OPAL_2000_I529898 : public Analysis {
15  public:
16
17    RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2000_I529898);
18
19
20    /// @name Analysis methods
21    /// @{
22
23    void init() {
24      declare(Beam(), "Beams");
25      declare(ChargedFinalState(), "FS");
26      declare(UnstableParticles(), "UFS");
27      book(_histXeK0   , 3, 1, 1);
28    }
29
30
31    void analyze(const Event& e) {
32      // First, veto on leptonic events by requiring at least 4 charged FS particles
33      const FinalState& fs = apply<FinalState>(e, "FS");
34      const size_t numParticles = fs.particles().size();
35
36      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
37      if (numParticles < 2) {
38        MSG_DEBUG("Failed leptonic event cut");
39        vetoEvent;
40      }
41      MSG_DEBUG("Passed leptonic event cut");
42
43      // Get beams and average beam momentum
44      const ParticlePair& beams = apply<Beam>(e, "Beams").beams();
45      const double meanBeamMom = ( beams.first.p3().mod() +
46                                   beams.second.p3().mod() ) / 2.0;
47      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
48
49      // Final state of unstable particles to get particle spectra
50      const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");
51
52      for (const Particle& p : ufs.particles()) {
53        const int id = p.abspid();
54        if (id == PID::K0S || id == PID::K0L) {
55          double xE = p.E()/meanBeamMom;
56          _histXeK0->fill(xE);
57        }
58      }
59    }
60
61
62    /// Finalize
63    void finalize() {
64      scale(_histXeK0, 1./sumOfWeights());
65    }
66
67    /// @}
68
69
70  private:
71
72    /// Histogram
73    Histo1DPtr _histXeK0;
74
75  };
76
77
78
79  RIVET_DECLARE_ALIASED_PLUGIN(OPAL_2000_I529898, OPAL_2000_S4418603);
80
81}