Rivet analyses

title: TOPAZ_1989_I279575

Energy-energy correlation at $E_{\text{CMS}}=53.3$ and $59.5$ GeV

Experiment: TOPAZ (Tristan)

Inspire ID: 279575

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B227 (1989) 495-500, 1989

Beams: e- e+

Beam energies: (26.6, 26.6); (29.8, 29.8)GeV

Run details: - e+ e- to hadrons.

Measurement of the energy-energy correlation, and its assymetry in $e^+e^-$ collisions by TOPAZ at 53.3 and 59.5 GeV.

Source code:TOPAZ_1989_I279575.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class TOPAZ_1989_I279575 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TOPAZ_1989_I279575);


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

/// Book histograms and initialise projections before the run
void init() {


  // Initialise and register projections
  declare(FinalState(), "FS");

  // Book histograms
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    bool offset(en == "59500"s);
    book(_h[en + "eec"], 1 + offset, 1, 1);
    book(_h[en + "eecpi"], 1 + offset, 1, 2);
    book(_h[en + "aeec"], 1 + offset, 1, 3);
    book(_c[en], "TMP/weightSum_" + en);
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // First, veto on leptonic events by requiring at least 4 charged FS particles
  const FinalState& fs = apply<FinalState>(event, "FS");
  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  if (fs.particles().size() < 2) vetoEvent;
  _c[_sqs]->fill();

  const double Evis2 = sqr(sum(fs.particles(), Kin::E, 0.0));
  // (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->mom().p3();
      const Vector3 mom3_j = p_j->mom().p3();
      const double energy_i = p_i->mom().E();
      const double energy_j = p_j->mom().E();
      const double thetaij = mom3_i.unit().angle(mom3_j.unit()) / M_PI * 180.;
      double eec = (energy_i * energy_j) / Evis2;
      if (p_i != p_j) eec *= 2.;
      if (thetaij < 90.) {
        _h[_sqs + "eec"]->fill(thetaij, eec);
        _h[_sqs + "aeec"]->fill(thetaij, -eec);
      }
      else {
        _h[_sqs + "eecpi"]->fill(180. - thetaij, eec);
        _h[_sqs + "aeec"]->fill(180. - thetaij, eec);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_c, crossSectionPerEvent());
  scale(_h, crossSectionPerEvent());
  for (const auto& item : _c) {
    if (isZero(item.second->sumW())) continue;
    scale(_h[item.first + "eec"], 180.0 / M_PI / item.second->sumW());
    scale(_h[item.first + "eecpi"], 180.0 / M_PI / item.second->sumW());
    scale(_h[item.first + "aeec"], 180.0 / M_PI / item.second->sumW());
  }
}

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
map<string, CounterPtr> _c;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(TOPAZ_1989_I279575); } ```