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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
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Thrust.hh"
  4#include "Rivet/Projections/Sphericity.hh"
  5#include "Rivet/Projections/ChargedFinalState.hh"
  6
  7namespace Rivet {
  8
  9
 10  class TASSO_1990_S2148048 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1990_S2148048);
 15
 16
 17    /// @name Analysis methods
 18    //@{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      const ChargedFinalState cfs(Cuts::pT >=  0.1/GeV);
 23      declare(cfs, "CFS");
 24
 25      // Thrust and sphericity
 26      declare(Thrust(cfs), "Thrust");
 27      declare(Sphericity(cfs), "Sphericity");
 28
 29      // Histos
 30      int offset = 0;
 31      switch (int(sqrtS()/GeV)) {
 32        case 14:
 33          offset = 0;
 34          break;
 35        case 22:
 36          offset = 1;
 37          break;
 38        case 35:
 39          offset = 2;
 40          break;
 41        case 44:
 42          offset = 3;
 43          break;
 44      }
 45      book(_h_xp[0]      , 2, 1, 1+offset);
 46      book(_h_xp[1]      , 3, 1, 1+offset);
 47      book(_h_xi         , 4, 1, 1+offset);
 48      book(_h_pT         , 5, 1, 1+offset);
 49      book(_h_sphericity , 6, 1, 1+offset);
 50      book(_h_aplanarity , 7, 1, 1+offset);
 51      book(_h_thrust     , 8, 1, 1+offset);
 52      book(_sumWPassed,"/TMP/_sumWPassed");
 53    }
 54
 55
 56    /// Perform the per-event analysis
 57    void analyze(const Event& event) {
 58      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
 59
 60      // TASSO hadronic event selection TODO: move this into a trigger definition
 61      // See page 2 in publication
 62      // Condition 1)  --- require at least 5 (4) 'good' tracks
 63      int nch = cfs.particles().size();
 64      if ( (int(sqrtS()/GeV) > 27 && nch < 5) || (int(sqrtS()/GeV) <= 27 && nch < 4 ) ) {
 65        MSG_DEBUG("Failed # good tracks cut: " << nch);
 66        vetoEvent;
 67      }
 68      // Condition 2) ---
 69      // Condition 5) --- scalar momentum (not pT!!!) sum >= 0.265*s
 70      double momsum = 0.0;
 71      for (const Particle& p : cfs.particles()) {
 72        const double mom = p.p3().mod();
 73        momsum += mom;
 74      }
 75      if (momsum <=0.265 * sqrtS()/GeV) {
 76        MSG_DEBUG("Failed pTsum cut: " << momsum << " < " << 0.265 * sqrtS()/GeV);
 77        vetoEvent;
 78      }
 79
 80      // Raise counter for events that pass trigger conditions
 81      _sumWPassed->fill();
 82
 83      const Thrust& thrust = apply<Thrust>(event, "Thrust");
 84      //const Vector3 & thrustAxis = thrust.thrustAxis ();
 85      //double theta = thrustAxis.theta();
 86      //if ( fabs(cos(theta)) >= 0.8 ) {
 87        //MSG_DEBUG("Failed thrust angle cut: " << fabs(cos(theta)));
 88        //vetoEvent;
 89      //}
 90
 91      const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");
 92
 93      // Fill histograms in order of appearance in paper
 94      for (const Particle& p : cfs.particles()) {
 95        // Get momentum and energy of each particle.
 96        const Vector3 mom3 = p.p3();
 97        // Scaled momenta.
 98        const double mom = mom3.mod();
 99        const double scaledMom = 2.*mom/sqrtS();
100        const double pTin = dot(mom3, sphericity.sphericityMajorAxis());
101        const double pTout = dot(mom3, sphericity.sphericityMinorAxis());
102	const double pT=sqrt(sqr(pTin)+sqr(pTout));
103        _h_xp[0]->fill(scaledMom);
104        _h_xp[1]->fill(scaledMom);
105	_h_xi   ->fill(-log(scaledMom));
106	_h_pT   ->fill(pT);
107      }
108      // event shapes
109      _h_sphericity->fill(sphericity.sphericity());
110      _h_aplanarity->fill(sphericity.aplanarity());
111      _h_thrust->fill(thrust.thrust());
112    }
113
114
115    /// Normalise histograms etc., after the run
116    void finalize() {
117      scale(_h_xp[0], 1./ *_sumWPassed);
118      scale(_h_xp[1], 1./ *_sumWPassed);
119      scale(_h_xi   , 1./ *_sumWPassed);
120      scale(_h_pT   , 1./ *_sumWPassed);
121      normalize(_h_sphericity);
122      normalize(_h_aplanarity);
123      normalize(_h_thrust    );
124    }
125
126    //@}
127
128
129  private:
130
131    /// @name Histograms
132    //@{
133    Histo1DPtr _h_xp[2], _h_xi, _h_pT, _h_sphericity, _h_aplanarity, _h_thrust;
134    CounterPtr _sumWPassed;
135    //@}
136
137
138  };
139
140
141
142  RIVET_DECLARE_ALIASED_PLUGIN(TASSO_1990_S2148048, TASSO_1990_I294755);
143
144}