Rivet analyses

title: MARKII_1985_I216850

Charge Particle Distributions in Nearly Symmetric 3 Jet Events at 29 GeV

Experiment: MARKII (MARKII)

Inspire ID: 216850

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 55 (1985) 1954

Beams: e+ e-

Beam energies: (14.5, 14.5)GeV

Run details: - e+ e- -> hadrons

Measurement of the fractional momentum of particles in 3 Nearly Symmetric 3 Jet Events at 29 GeV. Provides information on gluon jets

Source code:MARKII_1985_I216850.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/Sphericity.hh"

namespace Rivet {

/// @brief 3 jet events at 29 GeV class MARKII_1985_I216850 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1985_I216850);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  const FinalState fs;
  declare(fs, "FS");
  const ChargedFinalState cfs;
  declare(cfs, "CFS");
  Sphericity sphere(fs);
  declare(sphere, "Sphericity");
  FastJets jadeJets = FastJets(fs, JetAlg::JADE, -1, JetMuons::ALL, JetInvisibles::DECAY);
  declare(jadeJets, "JadeJets");
  // histos
  book(_h, 1, 1, 1);
  book(_njet, "TMP/njet");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // at least 5 charged particles
  const FinalState& cfs = apply<FinalState>(event, "CFS");
  if (cfs.particles().size() < 5) vetoEvent;
  // sphericity cuts
  const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");
  if (sphericity.lambda3() < 0.06 || sphericity.lambda2() - sphericity.lambda3() < 0.05) vetoEvent;
  // cluster particles using jet
  const FastJets& jadejet = apply<FastJets>(event, "JadeJets");
  Particles fs = apply<FinalState>(event, "FS").particles();
  PseudoJets pjets = jadejet.clusterSeq()->exclusive_jets(3);
  Jets jets = jadejet.mkJets(pjets, fs);
  Vector3 n[3];
  // loop over the jets
  for (unsigned int ix = 0; ix < jets.size(); ++ix) {
    if (jets[ix].constituents().size() < 3) vetoEvent;
    double energy = 0.;
    for (const Particle& p : jets[ix].constituents()) energy += p.E();
    if (energy < 2. * GeV) vetoEvent;
    n[ix] = jets[ix].mom().p3().unit();
  }
  vector<double> dot;
  dot.reserve(3);
  for (unsigned int ix = 0; ix < jets.size(); ++ix) {
    for (unsigned int iy = ix + 1; iy < jets.size(); ++iy) {
      dot.push_back(n[ix].dot(n[iy]));
      const double angle = acos(dot.back()) * 180. / M_PI;
      if (angle < 100 || angle > 140) vetoEvent;
    }
  }
  double Ejet[3];
  Ejet[0] = (sqrtS() * (dot[1] - dot[0] * dot[2])) / ((-1 + dot[0]) * (1 + dot[0] - dot[1] - dot[2]));
  Ejet[1] = (sqrtS() * (-(dot[0] * dot[1]) + dot[2])) / ((-1 + dot[0]) * (1 + dot[0] - dot[1] - dot[2]));
  Ejet[2] = (sqrtS() * (1 + dot[0])) / (1 + dot[0] - dot[1] - dot[2]);
  // now loop over jets
  for (unsigned int ix = 0; ix < 3; ++ix) {
    _njet->fill();
    for (const Particle& p : jets[ix].constituents()) {
      if (p.isCharged()) {
        _h->fill(p.momentum().p3().mod() / Ejet[ix]);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h, 1. / *_njet);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h;
CounterPtr _njet;
/// @}

};

RIVET_DECLARE_PLUGIN(MARKII_1985_I216850);

} ```