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Rivet analyses reference

CELLO_1982_I12010

Energy-Energy correlation at 22 and 34 GeV
Experiment: CELLO (Petra)
Inspire ID: 12010
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C14 (1982) 95, 1982
Beams: e+ e-
Beam energies: (11.0, 11.0); (17.0, 17.0) GeV
Run details:
  • e+e- to hadrons at 22 and 34 GeV CMS. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Measurement of the energy-energy correlation, and its assymetry, at centre-of-mass energies 22 and 34 GeV Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Source code: CELLO_1982_I12010.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/FinalState.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief Add a short analysis description here
 10  class CELLO_1982_I12010 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(CELLO_1982_I12010);
 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      declare(FinalState(), "FS");
 24
 25      // Book histograms
 26      unsigned int iloc(0);
 27      if(isCompatibleWithSqrtS(22.)) {
 28	iloc=1;
 29      }
 30      else if (isCompatibleWithSqrtS(34.)) {
 31	iloc=2;
 32      }
 33      else
 34	MSG_ERROR("Beam energy not supported!");
 35      book(_histEEC  , 1, 1, iloc);
 36      book(_histAEEC , 3, 1, iloc);
 37      book(_weightSum, "TMP/weightSum");
 38
 39    }
 40
 41
 42    /// Perform the per-event analysis
 43    void analyze(const Event& event) {
 44      // First, veto on leptonic events by requiring at least 4 charged FS particles
 45      const FinalState& fs = apply<FinalState>(event, "FS");
 46      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
 47      if ( fs.particles().size() < 2) {
 48        MSG_DEBUG("Failed leptonic event cut");
 49        vetoEvent;
 50      }
 51      MSG_DEBUG("Passed leptonic event cut");
 52      _weightSum->fill();
 53
 54      double Evis = 0.0;
 55      for (const Particle& p : fs.particles()) {
 56        Evis += p.E();
 57      }
 58      double Evis2 = sqr(Evis);
 59      // (A)EEC
 60      // Need iterators since second loop starts at current outer loop iterator, i.e. no "foreach" here!
 61      for (Particles::const_iterator p_i = fs.particles().begin(); p_i != fs.particles().end(); ++p_i) {
 62        for (Particles::const_iterator p_j = p_i; p_j != fs.particles().end(); ++p_j) {
 63          const Vector3 mom3_i = p_i->momentum().p3();
 64          const Vector3 mom3_j = p_j->momentum().p3();
 65          const double energy_i = p_i->momentum().E();
 66          const double energy_j = p_j->momentum().E();
 67          const double thetaij = mom3_i.unit().angle(mom3_j.unit());
 68          double eec = (energy_i*energy_j) / Evis2;
 69	  if(p_i != p_j) eec *= 2.;
 70          _histEEC->fill(thetaij, eec);
 71          if (thetaij <0.5*M_PI)
 72            _histAEEC->fill( thetaij, -eec);
 73          else
 74            _histAEEC->fill( M_PI-thetaij, eec);
 75        }
 76      }
 77    }
 78
 79
 80    /// Normalise histograms etc., after the run
 81    void finalize() {
 82      scale(_histEEC,  1.0/ *_weightSum);
 83      scale(_histAEEC, 1.0/ *_weightSum);
 84    }
 85
 86    //@}
 87
 88
 89    /// @name Histograms
 90    //@{
 91    Histo1DPtr _histEEC, _histAEEC;
 92    CounterPtr _weightSum;
 93    //@}
 94
 95
 96  };
 97
 98
 99  // The hook for the plugin system
100  RIVET_DECLARE_PLUGIN(CELLO_1982_I12010);
101
102
103}