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ALEPH_2002_S4823664

$\eta$ and $\omega$ Production in Hadronic $Z^0$ Decays
Experiment: OPAL (LEP 1)
Inspire ID: 569165
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B528 (2002) 19-33
  • hep-ex/0201012
Beams: e+ e-
Beam energies: (45.6, 45.6) GeV
Run details:
  • Hadronic Z decay events generated on the Z pole ($\sqrt{s} = 91.2$ GeV)

The production of $\eta$ and $\omega$ mesons measured using 4 million $Z^0$ events by the ALEPH experiment at LEP. Only the fragmentation functions are implemented.

Source code: ALEPH_2002_S4823664.cc
 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 ALEPH eta/omega fragmentation function paper
12  ///
13  /// @author Peter Richardson
14  class ALEPH_2002_S4823664 : public Analysis {
15  public:
16
17    RIVET_DEFAULT_ANALYSIS_CTOR(ALEPH_2002_S4823664);
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(_histXpEta   , 2, 1, 2);
28      book(_histXpOmega , 3, 1, 2);
29    }
30
31
32    void analyze(const Event& e) {
33      // First, veto on leptonic events by requiring at least 4 charged FS particles
34      const FinalState& fs = apply<FinalState>(e, "FS");
35      const size_t numParticles = fs.particles().size();
36
37      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
38      if (numParticles < 2) {
39        MSG_DEBUG("Failed leptonic event cut");
40        vetoEvent;
41      }
42      MSG_DEBUG("Passed leptonic event cut");
43
44      // Get beams and average beam momentum
45      const ParticlePair& beams = apply<Beam>(e, "Beams").beams();
46      const double meanBeamMom = ( beams.first.p3().mod() +
47                                   beams.second.p3().mod() ) / 2.0;
48      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
49
50      // Final state of unstable particles to get particle spectra
51      const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");
52
53      for (const Particle& p : ufs.particles()) {
54        if(p.abspid()==221) {
55          double xp = p.p3().mod()/meanBeamMom;
56          _histXpEta->fill(xp);
57        }
58        else if(p.abspid()==223) {
59          double xp = p.p3().mod()/meanBeamMom;
60          _histXpOmega->fill(xp);
61        }
62      }
63    }
64
65
66    void finalize() {
67      scale(_histXpEta  , 1./sumOfWeights());
68      scale(_histXpOmega, 1./sumOfWeights());
69    }
70
71    /// @}
72
73
74  private:
75
76    Histo1DPtr _histXpEta;
77    Histo1DPtr _histXpOmega;
78
79  };
80
81
82  RIVET_DECLARE_ALIASED_PLUGIN(ALEPH_2002_S4823664, ALEPH_2002_I569165);
83
84}