Rivet analyses

title: OPAL_2003_I595335

Charged particle momentum spectra in $e^+e^-$ annihilation at $\sqrt{s}= 192 $ GeV to $209$ GeV

Experiment: OPAL (LEP2)

Inspire ID: 595335

Status: VALIDATED

Authors: - Peter Richardson

References: - Eur.Phys.J. C27 (2003) 467-481

Beams: e+ e-

Beam energies: (101.0, 101.0)GeV

Run details: - Hadronic $e^+ e^-$ events at 202 GeV.

Measurement of charged particle distributions in $e^+e^-$ annihilation at $\sqrt{s}= 192 $ GeV to $209$ GeV.

Source code:OPAL_2003_I595335.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/Thrust.hh"

namespace Rivet {

/// @brief Add a short analysis description here class OPAL_2003_I595335 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2003_I595335);


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

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

  // Initialise and register projections
  declare(Beam(), "Beams");
  const ChargedFinalState cfs = ChargedFinalState();
  declare(cfs, "CFS");
  declare(Thrust(cfs), "Thrust");

  book(_h_pT_in, 1, 1, 1);
  book(_h_pT_out, 2, 1, 1);
  book(_h_y, 3, 1, 1);
  book(_h_x, 4, 1, 1);
  book(_h_xi, 5, 1, 1);
  book(_wSum, "TMP/wSum");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // First, veto on leptonic events by requiring at least 4 charged FS particles
  const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
  const size_t numParticles = cfs.particles().size();
  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  if (numParticles < 2) {
    MSG_DEBUG("Failed leptonic event cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed leptonic event cut");
  _wSum->fill();

  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
  const double meanBeamMom = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
  MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
  // Thrusts
  MSG_DEBUG("Calculating thrust");
  const Thrust& thrust = apply<Thrust>(event, "Thrust");
  for (const Particle& p : cfs.particles()) {
    const Vector3 mom3 = p.p3();
    const double energy = p.E();
    const double pTinT = dot(mom3, thrust.thrustMajorAxis());
    const double pToutT = dot(mom3, thrust.thrustMinorAxis());
    _h_pT_in->fill(fabs(pTinT / GeV));
    _h_pT_out->fill(fabs(pToutT / GeV));
    const double momT = dot(thrust.thrustAxis(), mom3);
    const double rapidityT = 0.5 * std::log((energy + momT) / (energy - momT));
    _h_y->fill(fabs(rapidityT));
    const double mom = mom3.mod();
    const double scaledMom = mom / meanBeamMom;
    const double logInvScaledMom = -std::log(scaledMom);
    _h_xi->fill(logInvScaledMom);
    _h_x->fill(scaledMom);
  }
}


/// Normalise histograms etc., after the run
void finalize() {

  scale(_h_pT_in, 1. / *_wSum);
  scale(_h_pT_out, 1. / *_wSum);
  scale(_h_y, 1. / *_wSum);
  scale(_h_x, 1. / *_wSum);
  scale(_h_xi, 1. / *_wSum);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pT_in, _h_pT_out, _h_y, _h_x, _h_xi;
CounterPtr _wSum;
/// @}

};

RIVET_DECLARE_PLUGIN(OPAL_2003_I595335);

} ```