Rivet Analyses Reference

TASSO_1990_S2148048

Event shapes in $e^+ e^-$ annihilation at 14--44 GeV
Experiment: TASSO (PETRA)
Inspire ID: 294755
Status: VALIDATED
Authors:
  • Holger Schulz
References:
  • Z.Phys.C47:187-198,1990
  • DESY-90-013
Beams: e- e+
Beam energies: (7.0, 7.0); (11.0, 11.0); (17.5, 17.5); (21.9, 21.9) GeV
Run details:
  • $e^+ e^- \to \text{jet jet}$ (+ jets). Kinematic cuts such as CKIN(1) in Pythia need to be set slightly below the CMS energy.

Event shapes Thrust, Sphericity, Aplanarity and charged particle spectra at four different energies

Source code: TASSO_1990_S2148048.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Thrust.hh"
#include "Rivet/Projections/Sphericity.hh"
#include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {


  class TASSO_1990_S2148048 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1990_S2148048);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      const ChargedFinalState cfs(Cuts::pT >=  0.1/GeV);
      declare(cfs, "CFS");

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

      // Histos
      int offset = 0;
      switch (int(sqrtS()/GeV)) {
        case 14:
          offset = 0;
          break;
        case 22:
          offset = 1;
          break;
        case 35:
          offset = 2;
          break;
        case 44:
          offset = 3;
          break;
      }
      book(_h_xp[0]      , 2, 1, 1+offset);
      book(_h_xp[1]      , 3, 1, 1+offset);
      book(_h_xi         , 4, 1, 1+offset);
      book(_h_pT         , 5, 1, 1+offset);
      book(_h_sphericity , 6, 1, 1+offset);
      book(_h_aplanarity , 7, 1, 1+offset);
      book(_h_thrust     , 8, 1, 1+offset);
      book(_sumWPassed,"/TMP/_sumWPassed");
    }


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

      // TASSO hadronic event selection TODO: move this into a trigger definition
      // See page 2 in publication
      // Condition 1)  --- require at least 5 (4) 'good' tracks
      int nch = cfs.particles().size();
      if ( (int(sqrtS()/GeV) > 27 && nch < 5) || (int(sqrtS()/GeV) <= 27 && nch < 4 ) ) {
        MSG_DEBUG("Failed # good tracks cut: " << nch);
        vetoEvent;
      }
      // Condition 2) ---
      // Condition 5) --- scalar momentum (not pT!!!) sum >= 0.265*s
      double momsum = 0.0;
      for (const Particle& p : cfs.particles()) {
        const double mom = p.p3().mod();
        momsum += mom;
      }
      if (momsum <=0.265 * sqrtS()/GeV) {
        MSG_DEBUG("Failed pTsum cut: " << momsum << " < " << 0.265 * sqrtS()/GeV);
        vetoEvent;
      }

      // Raise counter for events that pass trigger conditions
      _sumWPassed->fill();

      const Thrust& thrust = apply<Thrust>(event, "Thrust");
      //const Vector3 & thrustAxis = thrust.thrustAxis ();
      //double theta = thrustAxis.theta();
      //if ( fabs(cos(theta)) >= 0.8 ) {
        //MSG_DEBUG("Failed thrust angle cut: " << fabs(cos(theta)));
        //vetoEvent;
      //}

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

      // Fill histograms in order of appearance in paper
      for (const Particle& p : cfs.particles()) {
        // Get momentum and energy of each particle.
        const Vector3 mom3 = p.p3();
        // Scaled momenta.
        const double mom = mom3.mod();
        const double scaledMom = 2.*mom/sqrtS();
        const double pTin = dot(mom3, sphericity.sphericityMajorAxis());
        const double pTout = dot(mom3, sphericity.sphericityMinorAxis());
	const double pT=sqrt(sqr(pTin)+sqr(pTout));
        _h_xp[0]->fill(scaledMom);
        _h_xp[1]->fill(scaledMom);
	_h_xi   ->fill(-log(scaledMom));
	_h_pT   ->fill(pT);
      }
      // event shapes
      _h_sphericity->fill(sphericity.sphericity());
      _h_aplanarity->fill(sphericity.aplanarity());
      _h_thrust->fill(thrust.thrust());
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_xp[0], 1./ *_sumWPassed);
      scale(_h_xp[1], 1./ *_sumWPassed);
      scale(_h_xi   , 1./ *_sumWPassed);
      scale(_h_pT   , 1./ *_sumWPassed);
      normalize(_h_sphericity);
      normalize(_h_aplanarity);
      normalize(_h_thrust    );
    }

    //@}


  private:

    /// @name Histograms
    //@{
    Histo1DPtr _h_xp[2], _h_xi, _h_pT, _h_sphericity, _h_aplanarity, _h_thrust;
    CounterPtr _sumWPassed;
    //@}


  };



  RIVET_DECLARE_ALIASED_PLUGIN(TASSO_1990_S2148048, TASSO_1990_I294755);

}