Rivet analyses

title: PLUTO_1981_I156315

Energy-Energy correlation for a range of energies between 7.7 and 31.6 GeV

Experiment: PLUTO (DORIS/Petra)

Inspire ID: 156315

Status: VALIDATED

Authors: - Peter Richardson

References: none listed

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons at 7.7,9.4,12.,13.,17.,22.,27.6,30.0-31.6 GeV CMS

Measurement of the energy-energy correlation, and its assymetry, or a range of energies between 7.7 and 31.6 GeV.

Source code:PLUTO_1981_I156315.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief EEC for a wide range of energies class PLUTO_1981_I156315 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(PLUTO_1981_I156315);


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

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

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

  // Book histograms
  size_t ih = 1;
  for (double eVal : {7.7, 9.4, 12., 13., 17., 22., 27.6}) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    book(_h[en], 1, 1, ih);
    book(_c[en], "TMP/weightSum_" + en);
    ++ih;
  }
  book(_h["-"], 1, 1, ih);
  book(_c["-"], "TMP/weightSum");
  book(_h["lo"], 4, 1, 1);
  book(_h["hi"], 5, 1, 1);
  if (_sqs.empty() && inRange(sqrtS(), 30.0, 31.6)) _sqs = "-";
  raiseBeamErrorIf(_sqs.empty());

  if (_sqs == "7700"s || _sqs == "9400"s)
    _aeec = "lo";
  else if (_sqs == "27600"s || _sqs == "-"s)
    _aeec = "hi";
}


/// 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) {
    MSG_DEBUG("Failed leptonic event cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed leptonic event cut");
  _c[_sqs]->fill();

  const double Evis = 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) / Evis;
      if (p_i != p_j) eec *= 2.;
      _h[_sqs]->fill(thetaij, eec);
      if (!_aeec.empty()) {
        if (thetaij < 90.) {
          _h[_aeec]->fill(thetaij, -eec);
        }
        else {
          _h[_aeec]->fill(180. - thetaij, eec);
        }
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (const auto& item : _c) {
    const double w = item.second->val();
    if (isZero(w)) continue;
    scale(_h[item.first], 360.0 / M_PI / w);
  }
  // If both energies have been run, then the merging behaviour is not well defined
  const double losum = _c["7700"s]->sumW() + _c["9400"s]->sumW();
  if (!isZero(losum)) scale(_h["lo"], 360.0 / M_PI / losum);
  const double hisum = _c["27600"s]->sumW() + _c["-"s]->sumW();
  if (!isZero(hisum)) scale(_h["hi"], 360.0 / M_PI / hisum);
}

/// @}

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

};

RIVET_DECLARE_PLUGIN(PLUTO_1981_I156315);

} ```