Rivet analyses

title: TASSO_1987_I248660

Energy-Energy correlations between 12 and 46.8 GeV

Experiment: TASSO (Petra)

Inspire ID: 248660

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C36 (1987) 349-361, 1987

Beams: e+ e-

Beam energies: (7.0, 7.0); (11.0, 11.0); (17.4, 17.4); (21.8, 21.8)GeV

Run details: - e+e- to hadrons at the relevant CMS energies.

Measurement of the energy-energy correlation at centre-of-mass energies between 12 and 46.8 GeV.

Source code:TASSO_1987_I248660.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief for 14,22,34.8 and 43.5 GeV class TASSO_1987_I248660 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1987_I248660);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");

  // Book histograms
  size_t ih = 1;
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    book(_h[en], ih, 1, 1);
    book(_c[en], "TMP/weightSum" + en);
    ++ih;
  }
  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->p3();
      const Vector3 mom3_j = p_j->p3();
      const double energy_i = p_i->E();
      const double energy_j = p_j->E();
      const double cosij = dot(mom3_i.unit(), mom3_j.unit());
      double eec = (energy_i * energy_j) / Evis2;
      if (p_i != p_j) eec *= 2.0;
      _h[_sqs]->fill(cosij, eec);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (const auto& item : _c) {
    scale(_h[item.first], 1.0 / item.second->sumW());
  }
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(TASSO_1987_I248660); } ```