Rivet analyses

title: MARKII_1988_I250899

Energy-energy correlation at 29 GeV

Experiment: MARKII (PEP)

Inspire ID: 250899

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.D 37 (1988) 3091, 1988

Beams: e+ e-

Beam energies: (14.5, 14.5)GeV

Run details: - e+e- to hadrons

Energy-Energy correlation and its asymmetry measured at 29 GeV by the MARKII collaboration.

Source code:MARKII_1988_I250899.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief EEC at 29 GeV class MARKII_1988_I250899 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1988_I250899);


/// @name Analysis methods
///@{

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h_EEC[ix], 2 * ix + 1, 1, 1);
    book(_h_AEEC[ix], 2 * ix + 2, 1, 1);
  }
  book(_weightSum, "TMP/weightSum");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  if (fs.particles().size() < 2) vetoEvent;
  _weightSum->fill();
  // visible energy
  double Evis = 0.0;
  for (const Particle& p : fs.particles()) {
    Evis += p.E();
  }
  double Evis2 = sqr(Evis);
  // (A)EEC
  // Need iterators since second loop starts at current outer loop iterator, i.e. no "foreach" here!
  for (Particles::const_iterator p_i = fs.particles().begin(); p_i != fs.particles().end(); ++p_i) {
    for (Particles::const_iterator p_j = p_i; p_j != fs.particles().end(); ++p_j) {
      const Vector3 mom3_i = p_i->momentum().p3();
      const Vector3 mom3_j = p_j->momentum().p3();
      const double energy_i = p_i->momentum().E();
      const double energy_j = p_j->momentum().E();
      const double thetaij = 180. * mom3_i.unit().angle(mom3_j.unit()) / M_PI;
      double eec = (energy_i * energy_j) / Evis2;
      if (p_i != p_j) eec *= 2.;
      for (unsigned int ix = 0; ix < 3; ++ix) _h_EEC[ix]->fill(thetaij, eec);
      if (thetaij < 90.)
        for (unsigned int ix = 0; ix < 3; ++ix) _h_AEEC[ix]->fill(thetaij, -eec);
      else
        for (unsigned int ix = 0; ix < 3; ++ix) _h_AEEC[ix]->fill(180. - thetaij, eec);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) {
    // factor due angle in degress not radians
    scale(_h_EEC[ix], 180.0 / M_PI / *_weightSum);
    scale(_h_AEEC[ix], 180.0 / M_PI / *_weightSum);
  }
}

///@}


/// @name Histograms
///@{
Histo1DPtr _h_EEC[3], _h_AEEC[3];
CounterPtr _weightSum;
///@}

};

RIVET_DECLARE_PLUGIN(MARKII_1988_I250899);

} ```