rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

MAC_1985_I202924

Energy-Energy correlation at $E_{\text{CMS}}=29$ GeV
Experiment: MAC (PEP)
Inspire ID: 202924
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D31 (1985) 2724, 1985
Beams: e- e+
Beam energies: (14.5, 14.5) GeV
Run details:
  • e+ e- to hadrons

Measurement of the energy-energy correlation, and its assymetry in $e^+e^-$ collisions by MAC at 29 GeV.

Source code: MAC_1985_I202924.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief EEC at 29 GeV
 9  class MAC_1985_I202924 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(MAC_1985_I202924);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21
22      // Initialise and register projections
23      declare(FinalState(), "FS");
24
25      book(_histEEC   , 1, 1, 1);
26      book(_histEEC_Pi, 1, 1, 2);
27      book(_histAEEC  , 1, 1, 3);
28      book(_weightSum,"TMP/weightSum");
29
30    }
31
32
33    /// Perform the per-event analysis
34    void analyze(const Event& event) {
35      // First, veto on leptonic events by requiring at least 4 charged FS particles
36      const FinalState& fs = apply<FinalState>(event, "FS");
37      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
38      if ( fs.particles().size() < 2) {
39        MSG_DEBUG("Failed leptonic event cut");
40        vetoEvent;
41      }
42      MSG_DEBUG("Passed leptonic event cut");
43      _weightSum->fill();
44
45      double Evis = 0.0;
46      for( const Particle& p : fs.particles()) {
47        Evis += p.E();
48      }
49      double Evis2 = sqr(Evis);
50      // (A)EEC
51      // Need iterators since second loop starts at current outer loop iterator, i.e. no "foreach" here!
52      for (Particles::const_iterator p_i = fs.particles().begin(); p_i != fs.particles().end(); ++p_i) {
53        for (Particles::const_iterator p_j = p_i; p_j != fs.particles().end(); ++p_j) {
54          const Vector3 mom3_i = p_i->momentum().p3();
55          const Vector3 mom3_j = p_j->momentum().p3();
56          const double energy_i = p_i->momentum().E();
57          const double energy_j = p_j->momentum().E();
58          const double thetaij = mom3_i.unit().angle(mom3_j.unit())/M_PI*180.;
59          double eec = (energy_i*energy_j) / Evis2;
60	  if(p_i != p_j) eec *= 2.;
61          if (thetaij < 90.) {
62	    _histEEC ->fill(thetaij,  eec);
63            _histAEEC->fill(thetaij, -eec);
64	  }
65          else {
66	    _histEEC_Pi->fill(180.-thetaij, eec);
67            _histAEEC  ->fill(180.-thetaij, eec);
68	  }
69        }
70      }
71    }
72
73    /// Normalise histograms etc., after the run
74    void finalize() {
75      scale(_histEEC   , 180.0/M_PI*1000./ *_weightSum);
76      scale(_histEEC_Pi, 180.0/M_PI*1000./ *_weightSum);
77      scale(_histAEEC  , 180.0/M_PI*1000./ *_weightSum);
78    }
79
80    //@}
81
82    /// @name Histograms
83    //@{
84    Histo1DPtr _histEEC, _histEEC_Pi, _histAEEC;
85    CounterPtr _weightSum;
86    //@}
87
88  };
89
90
91  // The hook for the plugin system
92  RIVET_DECLARE_PLUGIN(MAC_1985_I202924);
93
94
95}