Rivet analyses

title: TASSO_1988_I263859

Event shapes at 35 GeV

Experiment: TASSO (Petra)

Inspire ID: 263859

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C41 (1988) 359-373, 1988

Beams: e- e+

Beam energies: (17.5, 17.5)GeV

Run details: - $e^+ e^- \to$hadrons

Event shapes Thrust, Sphericity, Aplanarity at 35 GeV

Source code:TASSO_1988_I263859.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/Sphericity.hh"

include "Rivet/Projections/Thrust.hh"

namespace Rivet {

/// @brief event shapes at 35 GeV class TASSO_1988_I263859 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1988_I263859);


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

/// Book histograms and initialise projections before the run
void init() {
  const ChargedFinalState cfs;
  declare(cfs, "CFS");

  // Thrust and sphericity
  declare(Beam(), "Beams");
  declare(Thrust(cfs), "Thrust");
  declare(Sphericity(cfs), "Sphericity");

  // Book histograms
  book(_h_sphericity, 1, 1, 1);
  book(_h_aplanarity, 2, 1, 1);
  book(_h_thrust, 3, 1, 1);
  book(_h_pTin2, 4, 1, 1);
  book(_h_pTout2, 5, 1, 1);
  book(_h_ncharged, 6, 1, 1);
  book(_h_pTin, 7, 1, 1);
  book(_h_pTout, 8, 1, 1);
  book(_h_pT, 9, 1, 1);
  book(_h_x, 10, 1, 1);
  book(_h_rap, 11, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");

  // 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;
  const Thrust& thrust = apply<Thrust>(event, "Thrust");
  const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");

  _h_sphericity->fill(sphericity.sphericity());
  _h_aplanarity->fill(sphericity.aplanarity());
  _h_thrust->fill(thrust.thrust());

  double pTin2sum(0.), pTout2sum(0.);
  for (const Particle& p : cfs.particles()) {
    // Get momentum and energy of each particle.
    const Vector3 mom3 = p.p3();
    const double energy = p.E();
    // Scaled momenta.
    const double mom = mom3.mod();
    const double scaledMom = mom / meanBeamMom;
    _h_x->fill(scaledMom);

    const double momS = dot(sphericity.sphericityAxis(), mom3);
    const double pTinS = dot(mom3, sphericity.sphericityMajorAxis());
    const double pToutS = dot(mom3, sphericity.sphericityMinorAxis());
    const double pT = sqrt(pow(pTinS, 2) + pow(pToutS, 2));
    const double rapidityS = 0.5 * std::log((energy + momS) / (energy - momS));

    pTin2sum += sqr(pTinS);
    pTout2sum += sqr(pToutS);

    _h_pTin->fill(abs(pTinS) / GeV);
    _h_pTout->fill(abs(pToutS) / GeV);
    _h_pT->fill(pT / GeV);
    _h_rap->fill(abs(rapidityS));
  }
  unsigned int nCharged = cfs.particles().size();
  _h_ncharged->fill(nCharged);
  if (nCharged) {
    _h_pTin2->fill(pTin2sum / nCharged);
    _h_pTout2->fill(pTout2sum / nCharged);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_sphericity, 1. / sumOfWeights());
  scale(_h_aplanarity, 1. / sumOfWeights());
  scale(_h_thrust, 1. / sumOfWeights());
  scale(_h_pTin2, 1. / sumOfWeights());
  scale(_h_pTout2, 1. / sumOfWeights());
  scale(_h_ncharged, 1000. / sumOfWeights());
  scale(_h_pTin, 1. / sumOfWeights());
  scale(_h_pTout, 1. / sumOfWeights());
  scale(_h_pT, 1. / sumOfWeights());
  scale(_h_x, 1. / sumOfWeights());
  scale(_h_rap, 1. / sumOfWeights());
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_sphericity, _h_aplanarity, _h_thrust, _h_pTin2, _h_pTout2, _h_pTin, _h_pTout, _h_pT, _h_x,
    _h_rap;
BinnedHistoPtr<int> _h_ncharged;
/// @}

};

RIVET_DECLARE_PLUGIN(TASSO_1988_I263859);

} ```