Rivet analyses

title: AMY_1995_I406129

Durham and Jade differential 2-jet rate at 57.7 GeV

Experiment: AMY (Tristan)

Inspire ID: 406129

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B355 (1995) 394-400

Beams: e- e+

Beam energies: (28.9, 28.9)GeV

Run details: - e+e- to hadrons

Measurement of the differential 2-jet rate in $e^+e^-$ collisions at $57.7$ GeV by the AMY Collaboration. The Durham algorithm, together with 3 variants of the JADE algorithm are used. The JADE E-scheme results are significantly different from the other approaches.

Source code:AMY_1995_I406129.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "fastjet/JadePlugin.hh"

namespace fastjet {

class P_scheme : public JetDefinition::Recombiner { public:

std::string description() const {
  return "";
}
void recombine(const PseudoJet& pa, const PseudoJet& pb, PseudoJet& pab) const {
  PseudoJet tmp = pa + pb;
  double E = sqrt(tmp.px() * tmp.px() + tmp.py() * tmp.py() + tmp.pz() * tmp.pz());
  pab.reset_momentum(tmp.px(), tmp.py(), tmp.pz(), E);
}
void preprocess(PseudoJet& p) const {
  double E = sqrt(p.px() * p.px() + p.py() * p.py() + p.pz() * p.pz());
  p.reset_momentum(p.px(), p.py(), p.pz(), E);
}
~P_scheme() { }

};

class E0_scheme : public JetDefinition::Recombiner { public:

std::string description() const {
  return "";
}
void recombine(const PseudoJet& pa, const PseudoJet& pb, PseudoJet& pab) const {
  PseudoJet tmp = pa + pb;
  double fact = tmp.E() / sqrt(tmp.px() * tmp.px() + tmp.py() * tmp.py() + tmp.pz() * tmp.pz());
  pab.reset_momentum(fact * tmp.px(), fact * tmp.py(), fact * tmp.pz(), tmp.E());
}
void preprocess(PseudoJet& p) const {
  double fact = p.E() / sqrt(p.px() * p.px() + p.py() * p.py() + p.pz() * p.pz());

  p.reset_momentum(fact * p.px(), fact * p.py(), fact * p.pz(), p.E());
}
~E0_scheme() { }

};

}

namespace Rivet {

/// @brief AMY jets at class AMY_1995_I406129 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(AMY_1995_I406129);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  FinalState fs;
  declare(fs, "FS");
  // Book histograms
  book(_h["jade_P"], 2, 1, 1);
  book(_h["jade_E"], 3, 1, 1);
  book(_h["jade_E0"], 6, 1, 1);
  book(_h["durham"], 4, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles particles = apply<FinalState>(event, "FS").particles();
  MSG_DEBUG("Num particles = " << particles.size());
  PseudoJets pjs;
  double mpi = .13957;
  for (const Particle& p : particles) {
    Vector3 mom = p.p3();
    double energy = p.E();
    if (PID::isCharged(p.pid())) {
      energy = sqrt(mom.mod2() + sqr(mpi));
    }
    else {
      double fact = energy / mom.mod();
      mom *= fact;
    }
    pjs.push_back(fastjet::PseudoJet(mom.x(), mom.y(), mom.z(), energy));
  }
  // durham
  fastjet::JetDefinition durDef(fastjet::ee_kt_algorithm, fastjet::E_scheme);
  fastjet::ClusterSequence durham(pjs, durDef);
  double y_23 = durham.exclusive_ymerge_max(2);
  size_t idx = durhamAxis.index(y_23);
  string label = idx > 0 && idx <= _h["durham"]->xEdges().size() ? _h["durham"]->xEdges()[idx - 1]
                                                                 : "OTHER";
  _h["durham"]->fill(label);
  // jade e-scheme
  fastjet::JetDefinition::Plugin* plugin = new fastjet::JadePlugin();
  fastjet::JetDefinition jadeEDef(plugin);
  jadeEDef.set_recombination_scheme(fastjet::E_scheme);
  fastjet::ClusterSequence jadeE(pjs, jadeEDef);
  y_23 = jadeE.exclusive_ymerge_max(2);
  idx = jadeAxis.index(y_23);
  label = idx > 0 && idx <= _h["jade_E"]->xEdges().size() ? _h["jade_E"]->xEdges()[idx - 1] : "OTHER";
  _h["jade_E"]->fill(label);
  // jade p-scheme
  fastjet::P_scheme p_scheme;
  fastjet::JetDefinition jadePDef(plugin);
  jadePDef.set_recombiner(&p_scheme);
  fastjet::ClusterSequence jadeP(pjs, jadePDef);
  y_23 = jadeP.exclusive_ymerge_max(2);
  idx = jadeAxis.index(y_23);
  label = idx > 0 && idx <= _h["jade_P"]->xEdges().size() ? _h["jade_P"]->xEdges()[idx - 1] : "OTHER";
  _h["jade_P"]->fill(label);
  // jade E0-scheme
  fastjet::E0_scheme e0_scheme;
  fastjet::JetDefinition jadeE0Def(plugin);
  jadeE0Def.set_recombiner(&e0_scheme);
  fastjet::ClusterSequence jadeE0(pjs, jadeE0Def);
  y_23 = jadeE0.exclusive_ymerge_max(2);
  idx = jadeAxis.index(y_23);
  label = idx > 0 && idx <= _h["jade_E0"]->xEdges().size() ? _h["jade_E0"]->xEdges()[idx - 1] : "OTHER";
  _h["jade_E0"]->fill(label);
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h, 1. / sumOfWeights());
  for (auto& hist : _h) {
    for (auto& b : hist.second->bins()) {
      const size_t idx = b.index();
      b.scaleW(hist.first == "durham" ? 1. / durhamAxis.width(idx) : 1. / jadeAxis.width(idx));
    }
  }
}

/// @}


/// @name Histograms
/// @{
map<string, BinnedHistoPtr<string>> _h;
YODA::Axis<double> jadeAxis{0.0, 0.01, 0.02, 0.03, 0.04,   0.05, 0.06, 0.07, 0.0825,
                            0.1, 0.12, 0.14, 0.16, 0.1825, 0.21, 0.24, 0.27, 0.3};
YODA::Axis<double> durhamAxis{0.0,    0.002, 0.004, 0.0065, 0.0115, 0.02,   0.03, 0.04, 0.05, 0.06, 0.07,
                              0.0825, 0.1,   0.12,  0.14,   0.16,   0.1825, 0.21, 0.24, 0.27, 0.3};
/// @}

};

RIVET_DECLARE_PLUGIN(AMY_1995_I406129);

} ```