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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*GeV)) {
 28        iloc=1;
 29      }
 30      else if (isCompatibleWithSqrtS(34*GeV)) {
 31        iloc=2;
 32      }
 33      else {
 34        MSG_ERROR("Beam energy not supported!");
 35      }
 36      book(_histEEC,   1, 1, iloc);
 37      book(_histAEEC,  3, 1, iloc);
 38      book(_weightSum, "TMP/weightSum");
 39    }
 40
 41
 42    /// Perform the per-event analysis
 43    void analyze(const Event& event) {
 44
 45      if (edges[0].empty())  edges[0] = _histEEC->xEdges();
 46      if (edges[1].empty())  edges[1] = _histAEEC->xEdges();
 47
 48      // First, veto on leptonic events by requiring at least 4 charged FS particles
 49      const FinalState& fs = apply<FinalState>(event, "FS");
 50      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
 51      if ( fs.particles().size() < 2) {
 52        MSG_DEBUG("Failed leptonic event cut");
 53        vetoEvent;
 54      }
 55      MSG_DEBUG("Passed leptonic event cut");
 56      _weightSum->fill();
 57
 58      double Evis = 0.0;
 59      for (const Particle& p : fs.particles()) {
 60        Evis += p.E();
 61      }
 62      double Evis2 = sqr(Evis);
 63      // (A)EEC
 64      // Need iterators since second loop starts at current outer loop iterator, i.e. no "foreach" here!
 65      for (Particles::const_iterator p_i = fs.particles().begin(); p_i != fs.particles().end(); ++p_i) {
 66        for (Particles::const_iterator p_j = p_i; p_j != fs.particles().end(); ++p_j) {
 67          const Vector3 mom3_i = p_i->momentum().p3();
 68          const Vector3 mom3_j = p_j->momentum().p3();
 69          const double energy_i = p_i->momentum().E();
 70          const double energy_j = p_j->momentum().E();
 71          const double thetaij = mom3_i.unit().angle(mom3_j.unit());
 72          double eec = (energy_i*energy_j) / Evis2;
 73          if (p_i != p_j)  eec *= 2.;
 74          _histEEC->fill(map2string(thetaij, 0), eec);
 75          if (thetaij < 0.5*M_PI) {
 76            _histAEEC->fill(map2string(thetaij, 1), -eec);
 77          }
 78          else {
 79            _histAEEC->fill(map2string(M_PI-thetaij, 1), eec);
 80          }
 81        }
 82      }
 83    }
 84
 85    string map2string(const double val, const size_t axis) const {
 86      const size_t idx = axes[axis].index(val);
 87      if (idx && idx <= edges[axis].size())  return edges[axis][idx];
 88      return "OTHER";
 89    }
 90
 91    /// Normalise histograms etc., after the run
 92    void finalize() {
 93      scale(_histEEC,  1.0/ *_weightSum);
 94      scale(_histAEEC, 1.0/ *_weightSum);
 95    }
 96
 97    /// @}
 98
 99
100    /// @name Histograms
101    /// @{
102    BinnedHistoPtr<string> _histEEC, _histAEEC;
103    vector<string> edges[2];
104    CounterPtr _weightSum;
105    YODA::Axis<double> axes[2] = { YODA::Axis<double>(50, 0.0, M_PI),
106                                   YODA::Axis<double>(24, 0.0628, 0.5*M_PI) };
107    /// @}
108
109
110  };
111
112  RIVET_DECLARE_PLUGIN(CELLO_1982_I12010);
113}